The computer i use to store all my files has recently started acting up.... It will spontaneously reboot, or sometimes just blank out (the power light and then eventually the hard drive light will go out, but the light on the cd burner will still remain on indicating it still has power) and often the computer will say... CMOS checksum error - Defaults loaded Press F1 to continue, del to enter setup... at the POST.
any ideas?

Check the system date and the battery on the mainboard.

Check if everything is still in the right position (maybe has the vibration of the harddisk shaked out your CPU ;-)

hmm... it does have 3 hard drives in it, but the cpu seems firm. Perhaps a bad power supply?
anyone?

If the machine has been around for a while, then power supply would be my first guess, it's pretty easy to diagnose by just hooking another one up to it and seeing if the problem continues, or if you want, you can fire it up and go into the bios of the mobo and see if the voltages are bouncing around or nowhere near 5 and 12 volts... if it was a brand new motherboard, then I would suspect a defective component on the board that heats up to a certain point and then fails. Seen that plenty of times, sometimes takes hours of operation before it happens (usually under load)... burning in new components properly can save you a lot of trouble...

As far as the CMOS thing goes, try another battery, but it's odd because the spontaneous reboot shouldn't have anything to do with the battery...

hmmm.. c health status (at powerup)

Current CPU TEMP. 30C/ 85F
Current System temp. 27C/ 80F
CURRENT CPUFAN speed 3723 RPM,3561,3640,3810,3996
Current CHSFAN speed 0RPM
Vcore 1.77 V
2.5V 2.52V
3.3V 3.35V
5V 5.05V,5.02V
12V 12.18V,12.12

The comma separated valuse are where muliple values were observed over time.

No I'ts not a new motherboard. it's (C) 1984-2000, a 1GHZ processor

whoa... the power light went off, but i'm still at the cmos screen!?

The voltages are within reason, but your cpu fan speed variance is rather unusual... run your hand over the surface of the case, especially on the right hand side where the sheet metal is just under the mobo... check for unusually warm spots... I think your mainboard may be dying. Reason I say so, is it is doing some weird stuff, and that can't all be attributed to the battery (they usually last more than 4 years). The power supply doesnt seem to be out to lunch... but I'd still try another one because it is a lot cheaper and simpler than replacing a mobo! The battery is a cheap simple fix as well, but I think your problem is bigger than that.

What brand/model is the mainboard?

I'd really suspect the mainboard as well.
It's the thing that controls your leds, after all -- and when mainboards get finicky, the reboots happen.

The checksum error is telling you that your bios user data is corrupt.
Another clue that the motherboard is failing.

I would definitely try the battery and power supply first, though

--Shade