Setup (2 days old):
AthlonXP 2700+
Asus A7N8X Deluxe 2.0.1004
1GB (2x512 twin) Corsair PC2700 TWINX1024-2700LLPT on dual-channel
PNY 64MB GeForce3
Western Digital 40GB 7200 (primary)
Western Digital 80GB 7200 (secondary)
Sony DRU-500A DVDRW (primary)
Lite-On 40x (slave)
Soundblaster Audigy Platinum
Maxtor PCI IDE Controller
Western Digital 80GB 7200 (primary, chan1 on PCI ctrl)
WindowsXP

Got a brand new Asus A7N8X w/ new Corsair mem and AthlonXP 2700+ and I wanted to overclocked for the first time. Went too high and changed too much at once and NO POST when trying to boot with too high of settings.

OK, no problem I thought... took out battery and reset CMOS. Battery back in, reset CMOS jumper to default and boot away. Boot and POST ok, "CMOS checksum error - Hit DEL to enter setup" yeayea, my CMOS is reset, no biggie, but AthlonXP 2700 reported as 1500, just like when I first installed the new processor (common for this board I've seen in reading many forums). Go into BIOS and set FSB to 166 and leave everything else default and save/exit. Restart... NO POST! Reset CMOS again.

Restart and same 1500 report. Instead this time I leave FSB at 100 and hit F1 to continue to boot Windows at 1500. Windows boots fine, slow of course, but no errors. I restart Windows and NO POST!!!

When I get a NO POST, Hard Drive IDE light goes solid for about 10 seconds then goes blank. No monitor signal, nothin.

Any help would great be appreciated :)

Man that's weird.. can't think of anything that could cause that except maybe you did something to the board when you "went too high". if your board has a setting in the bios called load optimized defaults, use that option and see what happens then go back in the bios and try changing it to 133 again. if it doesn't work i would try reformatting and reinstall windows at 100fsb then after it's finished try turning it back up to 133. if it don't work all i can say is buy a new motherboard.

Well, I fixed it. Strange solution... not quite sure why but this is what I did.

I reset the CMOS and left the computer shut down for 30+ minutes. When I came back, I took out ram stick in Slot2 and it booted up just fine. When I was setting new settings, I had knocked the DDR voltage up to 2.7 from 2.6, so maybe that had something to do with it. It was indeed very frustrating but a sigh of reliefe when it worked. I'm now back up and running :)

I would like to add that I had the same problem as you after trying to overclock my A7N8X (non-delux) where the system would only boot up immediately after clearing the CMOS into a XP 1500+ and would not allow me to reboot .... would lock up with IDE light on for 10 seconds. When it would boot it had a cmos checksum error and asked me F1 or DEL etc... (at least I could boot into 1500 though! hehe.. to research the internet for help :)

I did your trick (half hour of battery out and clear CMOS, and remove ram stick etc...) and it did not fix mine.

The way I fixed mine was I flashed the BIOS with most recent one from ASUS... 1006 PCB rev 2. The system was perfect afterward.

Just to summarize the steps required to flash bios:

1) Make sure you know your PCB version. In the bootup screen often it will be displaed something like "A7N8X2.0" (PCB 2.0 etc), or the PCB version is also listed between 2 of the PCI slots on the motherboard near the right-hand-side of them in small white text, next to big white text advertising the mobo :)

2) www.asus.com --> go to support, and download the bios files

3) make a DOS bootable floppy, copy AWDFLASH.EXE as well as your blablabla.BIN file to floppy.

4) reboot to A:\> prompt, type "awdflash" (no quotes), program will ask you for name of the .BIN file, type it, and away you go.