Ive had this problem for around 1year...
I had 4 hard disks b4, 2IDE and 2 SATA hooked up on my PD 2.8ghz/ 1GBram PC. Motherboard is ASUS p5ld2. Problem was windows would hang randomly, even im not running anything..so when it hangs(means mouse doesnt even move), i restart by pushing the restart button..then somehow my windows hard disk would be be dectected in BIOS along with 1 or 2 more HDs. I get around the problem by powering off and replugging the disks and sometimes it fixes it and sometimes not..So first i thought i was a faulty hard disk. So i bought 2 new SATA disks and changed around them..problem still exist..so then i thought my ASUS MB had a problem witht eh IDE bus, so i bought a gigabyte S3 board. Problem STILL exist. Now i onli have 2 SATA disks connected and the boot disk is NEW and the storage is around 8months old.. the funny part is all the time after the hanging-reboot process, my boot disk doesnt get detected when the storage one does..i leave on the windows one connected it would run fine..but once any other disks are connected, the boot disk would sometimes not get detected. Ive changed around so many HD so i don't think is HD problem...I had a geforce 6600 PCIE b4 and now i have a Radeon x1950 PCIE...would it be not enough power going thru to my devices...on the box of the x1950 card,it says 500w PSU recomended..

All of this changing around was done with the same case and power supply? Your PSU may be too small for what you are running. What are the specs on the PSU?

my PSU states the max power is 450W

Max. power means nothing. what are the individual ratings.

im not too sure bout the specs on PSUs. Which one would matter..ive been searching around this problem for ages and the only chance left is that my PSU is not giving enough power...apart from that, ill prbly have to blame my CPU

could anyone tell me if i need a stronger PSU or not....i dnt wanna go and waste more money on this problem...ive already bought 3HD, 1mobo and alot of time to figure this out

Post the EXACT model of the PSU and maybe we can help. The problem isn't likely to be your processor.

my PSU states the following:
AC INPUT:
Voltage- 115V~230V
Current- 6A 3A
Frequency- 50-60hz
DC OUTPUT:
+3.3V +5V +12V -5V -12V +5Vsb
30A 28A 20A 0.5A 0.5A 2.0A
MAX:
220W 240W 2.5W 6W 10W
MAX 432W MAX 18.5W
TOTAL MAX POWER 450W

It would help if you also mentioned the brand name of the PSU. There are reputable manufacturers & there are generic ones that tend to 'fib' about the specs.

Generally, the +12v is the most important rail. The CPU gets ALL it's power from the +12v. The other components that feed off the +12v are the optical drives, HDDs, all fans, & video cards. Part of that +12v comes thru the PCI-E slot & the rest is supplied thru the PCI-E plug (when required). I would say the X1950 is the back-breaker.

Even though card manufacturers recommend certain wattage PSU's, they should quantify it by listing an amperage requirement on the +12v or at least say "high quality 500W PSU". There are far too many $20 500W PSUs on the market that people get suckered into buying. A decent quality PSU will cost between $50-100, unless it's on sale or a rebate is involved.

my PSU is some generic brand i think. It has 2 fans and i bought it for AUD$40...
i swapped in an old 400W PSU and it seems to work ok atm....maybe my one was just faulty...cos apparently this morning it could onli boot with 1 HDD plugged and no other CDroms and HDDs..

It sounds like jam may be right about makers fudging the ratings. One point to make though. There must be a name on the PSU other than "generic brand".

the brand of the PSU is Tsumori...
is that a good brand?

I never heard of it myself. Where are you located in the world?

australia....maybe i just worn out my PSU...like it got faulty..
the PSU came with the case....and my case isnt anything like antec or thrmaltake...

I did a little googling and that brand of PSU sells for about $95-100 Australian dollars. I don't know how to equate that to US dollars but it doesn't seem to be cheap.
I went back and re-read your first post. Are you using 80 wire IDE cables? They will have colored ends. You need to be sure you don't turn them end for end either. Be sure the IDE HDrives are jumpered correctly. You could try swapping the power connectors around to see if there are defective ends on some. I have run into that. The crimps are not right. Also the power connectors (molex) are sometimes stiff and require a decent amount of force to seat properly. Going back to the PSU you could measure the current and voltage if you have access to a meter or possibly a local shop may have equipment to test it. lastly, is the recepticle you connect the computer to properly grounded? That is easy to check.

im not too sure about the point u mentioned above Othehil..i dnt have any IDE hard disks, their all SATA..
now im using a spare PSU and the problem seems to be gone....
would there be any chance that the PSU was just wearing out?
I mite be getting a new PSU with all the sata jacks on the PSU istead of using the molex cables

Sounds like the PSU may have been failing. Voltage surges like from lightning can do them in. I mentioned the IDE drive because in your first post you stated you had 2 connected. I understand you have moved things around. Turning cables 180 degees HAS been done before.