For that last couple of days there has been some reboots (just recovered from one) in XP since I switched to 512Meg DDR266 ram. If there was any random reboots before i switched to DDR ram (i originally had 256Meg PC133 ram), they are very rare and i can't remember any happening. Is the memory the problem? Could defective memory cause the reboots? Or is it something else? I know that XP has a protective feature that does reboots instead of BSOD. However, I don't know what is causing the reboots. The reboots occur seeming randomly, while I was using a program like before (the reboots never occur when I start a program, or end a program, or in any other reasonable places). I should probably also give the history of my computer. When i bought it, it had XP 1700+ on a PCChips M841L MoBo. However, the person who put the computer together forgot to clamp the CPU fan to the Mobo(!), and the fan fall off and the CPU got fried. I wasn't able to find the recipt and had to buy a new CPU, so I chose XP 2100+. The mobo seems to have survived the CPU burning, so i put the XP 2100+ on the Mobo. Everything seems to work fine until now, when there are seemingly random reboots that is destroying my work. Could it be the Mobo? Thanks for any help.

so youre mobo supports DDR and SDRAM? do you still have the 256MB stick? if so, replace to DDR with that to see if it's the RAM. If you've just got this problem after installing new RAM, the chances are that that is the culprit.

It's all pretty obscure, though, and I don't know how to reproduce the reboot. One thing I wanted to ask before I switch the RAM. I turned off Windows XP's automatic reboot feature, and was wondering what I would see if a fatal error appears again. Will Windows XP show a BSOD (Blue Screen of Death)? Or something else? How can I identify if an error occured that would lead to a reboot if the feature was turned on? Thanks.

a BSOD will usually appear. Numerous error messages on the screen, and all completely vague :)

most of the time, random reboots are the rsult of insuficient power. whats the wattage on your psu?

The wattage is 300W, powering XP 2100+ with one 40GB HD, a case fan, and the CPU fan, but nothing else (no PCI cards, etc.) I just encountered what i think would originally cause a reboot: My computer screen just goes blank (black, without BSOD), and to make it operating again, i have to press CTRL+ALT+DEL, which brings up the task manager. Everything was back to normal again except the application that i was just using, which became very sluggish, and with one interesting problem: when I move my mouse over the menu, the menu doesn't automatically highlight. When the program is restarted, everything is OK.

Also, the computer seems to lock up when using an CPU intensive application (ex. games).