just bought a new board today. pulled the agp from my old pc and computer will not display anything. i can hear the hard drive running, the agp fan is running, but my monitor light remains yellow. i pulled the card and tested in my old system and it works fine. the board has no onboard video. no error beeps or nothing.

99% of computer problems are not the motherboard nor power supply but simply between the keyboard and the chair.

here we go again...did you benchtest the board BEFORE installing it in the case?

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nope..assuming im not the only idiot whose done it then.

99% of computer problems are not the motherboard nor power supply but simply between the keyboard and the chair.

I preach this testing issue all the time. You should always confirm the board/CPU/RAM work together before installing them in the case. All those components should be assembled on the bench & mounted to the chassis outside the case anyway, so why not test them 1st? Obviously there's no point in going thru the hassle of mounting the assembly in the case if it's bad. If it bechtests good, go ahead & install it along with the video card, connect the case wiring, then test fire it again. If it checks out, THEN install any drives or cards.

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Hold on a minute.
There may be nothing wrong with your mboard and cpu, assuming you are using compatible ram in it (which is another subject) - it may not be booting because the video card is incompatible with it. You can't bench test it in that case.

Not enough information.
How old is your old mboard - what AGP modes does it support?
What AGP modes does your new mboard support?
What AGP modes does the video card support?
In what type of AGP slot can it be used in? (e.g. ATI's AGP cards are universal - can be used in several, but maybe not all, slot types).

Many recent mboards will not support an old 2X, or sometimes an old 4X, AGP card.
There are different types of AGP slots.
Not all AGP cards, even of the same rating, will work in all mboards.

Types of AGP slots:
http://www.ati.com/support/faq/agpchart.html
AGP vs AGP Pro
http://www.evga.com/articles/public.asp?AID=60

Oops - first link no longer works.
Types of AGP slots:
Go here:
https://support.ati.com/ics/support/default.asp?deptID=894
Type in Search Words box - agp slot types, click Go
Scroll down, see
737-18872: ATI AGP Graphics Cards - AGP Compliance Details

my card is an agp nvidia gforce 4 mx-420 64mb. my old mb is only a p3 1gig. from the chart on the link i was given above it seems my card works with the agp slot. apg card is type universal. mb type is 4x or 8x 1.5v. motherboard model ms-6791 from msi up to 3.?g. im running 2.6. i searched msi site for this board but it seems it doesnt exist. i also tried a different card but still no display

99% of computer problems are not the motherboard nor power supply but simply between the keyboard and the chair.

pull everything out of the case & start from scratch

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I searched the various MSI sites extensively, including archives - you're right - no MS-6791 anywhere.
Sometimes MSI neglects to put a model number in their searchable databases, but I do find it on the sites in obscure places, but not in this case, not even in these where I have found oddball models before:
http://www.msi.com.tw/html/products/mainboard/mb_htm/mb_comparison.pdf
http://www.msicomputer.com/product/p_archives.asp?class=mb

Since you didn't supply much other info, I searched on the web for MS-6791 - several hits.
It's available for as little as $24 US on E-Bay.

SiS648 Socket 478 P4
under picture
MB-SK-478-MS-6791-FX(1)

Specs
http://www.3btech.net/msi6740pe4mi.html
Supports Intel® Socket 478 for Pentium® 4 (Northwood) Processors
Cpu Support up to 3.2GHz/FSB 800
Supports FSB 400/533/800 MHz
Supports AGP 2.0 4x/8x.
Supports 64-bit high performance DDR333/DDR266 memory
Supports two 184-pin DDR DIMM.
LAN RealTek 8100C PHY.
Audio 6 channels software audio codec RealTek ALC655

note the msi6740pe4mi in the address
I tried searching the MSI sites with 6740 - no luck with that either.
Manual - link at the above - dead
http://www.microstar.com.cn/cgi/Download/Manual/MS-67xx/6791/6791v1.0.pdf
I even tried searching there - no luck.
You've got an orphan on your hands.

However, several other boards use the SiS 648 chipset.
The models are 648(whatever).
The AGP specs, ram requirements, and CPU support should be very similar if not identical.

For example - this one - a.k.a. MS-6585
Memory test report -
http://www.msi.com.tw/html/products/mainboard/testreport_pdf/6585/memory.pdf
VGA card test report
http://www.msi.com.tw/html/products/mainboard/testreport_pdf/6585/vga.pdf

" my card is an agp nvidia gforce 4 mx-420 64mb"
- a board with Nvidia GeForce 4 MX 420 works fine
So the card is probably not the problem.
.......

It isn't likely you have the wrong cpu, but just in case...
look at the cpu support lists.

The next most likely thing, assuming the motherboard, cpu, and your power supply (if you know it's good - tried it with something else) and it is are less likely to be a problem, is you are trying to use incompatible ram - that is VERY common!

I would look at the memory tests, and see if the ram you have is listed (not likely).
If you don't see the modules you have listed, go to the ram manufacturer's web site, or any ram manufacturer's web site (if it's generic ram you may have no web site to got to).
You can look up what will work for sure in your motherboard in most cases - if you can't find a listing for MS-6197, look up any of the other MSI models that have the SiS 648 chipset. You can often look up the specific specs of the ram - you can compare that to the specs of the ram you are trying to use.
You may be able to get the modules locally but memory listings often leave out the model numbers; you may have to order them.
OR - ask someone who has installed this board locally what ram they put in it that works - perhaps where you bought it?

okay, but lets say my ram isnt compatible, its ddr pc2100 non ecc...but wouldnt it still post or beep or something?

99% of computer problems are not the motherboard nor power supply but simply between the keyboard and the chair.

"just bought a new board today"

"motherboard model ms-6791....i searched msi site for this board but it seems it doesnt exist"

Are you 100% sure that model number is correct?

How about telling us WHERE you bought the board? Is it new or used? Did you buy it from an online vendor, eBay, a friend, at a store? Did it come with documentation?

If that model number is correct & you can't find it on the MSI website, it may be because it's not a retail product...it's probably an OEM board...& if that's the case, it's most likely a clone of a retail product. You'd have to figure out which one. Start by finding out what chipset is on the the board & whether it's an ATX or mATX board. That along will narrow it down considerably

Hellz Yea!

Another possibility is you don't have a P4 compliant PSU or you forgot to plug the 4-pin ATX12V1 plug into the board

Hellz Yea!

the peson who sold it advised me that celerons would run. however the description states that northwood p4 run on it. it is possible that i have the wrong cpu and he just wanted to sell a board?

99% of computer problems are not the motherboard nor power supply but simply between the keyboard and the chair.

"okay, but lets say my ram isnt compatible, its ddr pc2100 non ecc...but wouldnt it still post or beep or something?"

It might, it might not - it's common to have it not post.
Compatibilty is a lot more complicated than just the PCxxx number and whether it is ECC or non ECC.
(ECC is recommended if you have more than, say, 512mb total, but it's a lot more expensive.)
It might post but the amount of ram found by the computer is wrong.
You can have two ram modules that work fine individually, but will not work properly with each other, or even have a non-boot situation when both are installed. You can get a lot more detail at the major ram manufacturers web sites if you really want to dig that up, but it all boils down to some modules are compatible with a particular mboard, some are not, it varies from board to board, but is often consistant for a particular main chipset.
In trying to upgrade DIMM ram (SDRam mostly) on older computers I've personally had no posts, improper counts, and improper counts only when certain modules were used together. I've also found some mboards that were rated to take 128mb max in each slot will take 256mb ones if you use 16 chip 256's (8 each side), and I've gotten PC100 and less often PC133 128's to work on mboards originally designed for PC66 if you use 16 chip ones.
It isn't any less complicated now for your DDR and other newer ram, in fact it's probably more so.

Make sure you have a compatible CPU first - check out the CPU support charts of the similar models.

If you got the ram locally from a computer parts place, they very well may let you exchange it for ram modules that work - take your case assembly with you to test it on the spot; you may also need to take a monitor and keyboard - if they want to charge you to test the ram - you may have to do it yourself.

Yes, Jam, the model is correct. A search of the web finds it. It isn't the first time I've seen MSI lose track of a model - it doesn't matter if it is OEM or not, they did have support for it on their China site until not long ago. Gigabyte also sometimes does that.

I have not come across a ram module that was actually bad in many years. It is extremely reliable these days. It can be bad, but it is almost always caused by something else, such as a wonky PS that was supplying too much voltage to a mboard, or that shorted, or some other catastrophic disaster.

basically boils down to testing another ram and cpu. ill give that a shot before i buy a new mb. i just dont have a spare to test. jam and tubes youve been a help, if i didnt shave my head i would have pulled my hair out. tubes you probably have carpal tunnel now that you've replied so much, so i will respectfully end this post with a huge thanks to both. i might return the board anyway, just noticed they removed the serial from above the printer port. why would they do that anyway and post it as new....anyway thanks again.

99% of computer problems are not the motherboard nor power supply but simply between the keyboard and the chair.