Need help with windows 7 rebooting

I bought Windows 7 downloaded with no problems things seem to be ok except at least once a day my computer will reboot itself, what could be the problem

Thank You

Hi charliebird and welcome to Windows 7 Forums

There could be various reasons for the computer rebooting itself - software and hardware, have you installed any new hardware or software before this behaviour started ?. I would also check all cables to make sure all are seated right, Is your system overheating ? check all your fans and vents and take a look at your temps in BIOS. Faulty RAM can cause reboots its a good idea to check use Memtest > http://www.memtest.org/ or try > ttp://oca.microsoft.com/en/windiag.asp .A faulty PSU can cause reboots this can be tested with a multi meter.