For the past few months I've been running an Athlon XP-M 2500 on a MSI K7N2-Delta2 LSR. I have the latest bios installed, and had been happily running at 2.2 GHz (200 FSB x 11 mult) at 1.55 Vcore (+/- .025V, I don't recall exactly) for about 3 months. The CPU was sitting at around 48-50 C, but with summer coming on I thought I'd drop the multiplier lower to make sure things didn't get too hot. Long story short, as soon as I exited the bios setup the computer would no longer boot (fans start, lights blink, no POST). I cleared the CMOS and things came back, but now the best I can manage is 1.7 GHz (200 FSB x 8.5 mult) at 1.675 Vcore before it won't POST. I haven't seen what I can manage at 166 FSB, but I'm not too hopeful. I've run through the whole 'pull out everything non-essential and put them back one-by-one routine' to no avail (haven't checked RAM yet though). Any thoughts as to why this happened? Suggestions?

sys:
Win XP Pro SP2
Ath XP-M +2500
MSI K7N2-Delta2 LSR
1G pc3200 corsair value-ram (dual channeled)
400W antec PS
Sapphire Radeon 9600 256 meg RAM
2x DVD drives (1 R/W/RW)
1 floppy drive
2x case fans + 1 HS fan
1 low end Phillips sound card
60 WD HD w/ SATA adaptor

"I've run through the whole 'pull out everything non-essential and put them back one-by-one routine' to no avail"

Take em out & leave em out while you troubleshoot...you don't need to get into Windows, all you need to do is boot & get into the BIOS. You can try testing the RAM with memtest86, but if it worked OK before, I doubt it would just up & quit on you unless you overvolted it or something. What HSF are you using? Did you remove it, clean it & reapply paste?

Asus A7N8X-X
1800+ @ 8.5 x 200MHz
768MB PC3200 2.5-3-3-7
Asus A9550GE/TD 128MB
WinME/WinXP Pro

You might try this but I'm not sure if it will work. As a matter of fact, I don't even know for sure what CPC really is. lol!

CPC is synonymous with "Command Rate". Nforce2 boards run at 1t command rate by default. this gives great performance, but can cause instability when trying to run a high FSB with two double sided (most 512) dimms. So if that is a problem, try the CPC off or "2t" bios. It will allow for a higher FSB at the cost of memory performance.

YO

Thanks for the replies.
general update: I got the comp up to 166 x 12 = 1.99 GHz at 1.65 V at 42C (could probably get higher), but still no luck getting past 8.5 with 200 FSB.

jam: I'm using a copper HS w/fan that I got from CompUSA (could probably do better) with Artic Silver 5. I haven't tried removing and cleaning the HS yet (I'm a little hesitant to do so since the last time I did that I managed to kill my previous system), but it could be worth a shot. Could metallic dust really cause the system to unstable at 200 FSB, but fine at 166?
YOYO: I poked around my bios, but couldn't find any entry for CPC. Are there any other terms for it?
thanks again

Did you load fail safe defaults after you reset the bios?
Did you then load optimised defaults?

Have a look here...MSI Forum

Tt Lanfire
MSI K8N Diamond
AMD64 3000+'Winnie'
1gb pc4400
OCZ Powerstream 520w
6600GT
WDCaviar 160gb sata
WDCaviar 160gb sata

;~}