Hardware failure or system instability can cause the computer to reboot automatically. The problem could be the RAM, Hard Drive, Power Supply, Graphic Card or External devices: – or it could be an overheating or BIOS issue.

1. Go to the Search tool in your version of Windows, type sysdm.cpl, and select the program of the same name.

2. Click the Advanced tab.

3. Click the Settings button under Startup and Recovery (as opposed to the dialog box’s other two Settings buttons).

4. Uncheck Automatically restart.

5. You might also want to check Write an event to the system log if it’s not already checked.

OR

It could be a lot of things

1. Take off the computer cover, clean out the inside, check fans, then run the computer w/cover off.

2. Click on Start-Programs-Start Up. If there are any listings in the Start Up area, you need to delete as many as you can.(Right click the listing and choose 'Delete') Please remember that these are just shortcuts to programs and not actual program files, so its safe to delete them. Don't get rid of some that you really like like Microsoft Shortcut Bar or any others that you really want on the screen when it starts.

3. Then click on Start-Run, in the typing area put 'msconfig' (without the quotes), press Ok. When the System Configuration Utiltiy box opens, click on the Start Up tab. You will see a number of listings with boxes and check marks in them. These are programs that run at start up. You can safely uncheck many of the boxes. Don't uncheck System Tray, Scan Registry, or your Virus Scan startup programs. After you?re done, click 'Apply', then 0K, and the computer will ask you to restart. Do it and then check your resources again. Hopefully they are much higher.(Don't worry too much, if you make a mistake you can always go back to this box and put a check back in any of the listings you want)

If you have any questions about which programs to UNCHECK in 'msconfig', post back.

Hope this helps.