Thanks, I'll *monkey* around with it. =)

Did you check the event log for any strange errors?
 
Are this spontaneous reboots or can you see the "windows is shutting down" screen?
 
Try to disable advanced power management in the windows. It doesn't make a much difference what you set in the bios except the STR (suspend to ram) and POS (power on suspend).
 
Try to install "standard pc" instead of "ACPI computer". (can't remember how to do that)
 
Try to unplug the power switch from the motherboard and the green switch if you have one. It could be that they are buggy :x (just to exclude the possibility)
 
If this won't help, post back, we have some more.

Last night was probably the most worst night that XP kept on rebooting and restarting or throwing itself in Stand By mode.. and then turn the HD back on.. and then right away shut it off. When I unplugged the damn thing and then turned it back on, it went right to the BIOS and said an error that the CPU was hanging at an unexceptional BUS/PCI speed (I think it was BUS speed) and told me to readjust cuz it was running in SAFE MODE in the BIOS at 100 mhz. The BUS speed looked normal to me and the PCI speed was 133 mhz.. so I don't see any problems there. What I did last night was reformat my HD and reinstalled Windows and didn't install SP1. So far, no problems. No unusal reboots or anything. Oh and yes, these are spontaneous boots out of no where. Scares the crud outta me when it happens cuz I'm not use to it, lol. I'm at work now for the next 8 hrs (typical day right? lol) and then I see what I can do with it. If I come home and see that it has rebooted, then it's gotta be something internal. =)

Spontaneous reboots are mostly hardware's fault. Most often bad memory. But it could be anything. And that really sucks ;(

I assume that when you're referring to memory, you are talking about RAM correct? =) It's alright.. It's a 2 year old system that I built and I'm in the process of building a more top of the line system with new RAM of course and everything. Thanks. =)

if it is 2 years old could be the mobo / bios does not like Xp because of that ACPI or something like that? (pro's what is it called..lol) a protocol that XP uses............
 
 
i had that issue on an old pIII 600 - it would reboot often for no reason. - turens out the mobo was too old.

I don't think it's the motherboard because it's never given me a problem during the first year of release of XP. Only started to happen after I downloaded Service Pack 1. But who knows! LOL. It's alright, not a big problem. I'm in the process of building another desktop and I have a laptop anyway. Thanks for everyone's comments/help/suggestions.

I had the issue once i installed G6 ftp server and would copy files from one HD to another, or it would just do it if i tried to FXP to the ftp.

my computer also seems to be spontaneously rebooting, but there also seems to be a lot of hanging that didn't exist before. i'm wondering if this might be related to a mup.sys problem

This is a tip for everyone
 
 
Go to My Computer ---> Advanced ---> Start up and Recovery ---> In that tab uncheck the box that says Reboot Automatically
 
Now that your computer wont reboot automatically when it crashes you can see what the cause of the problem is.