My computer keeps shut down by itself, I just install win 7 X64 and brand new case cooler master HF922, it was working fine on vista 32 and right now every 5 or 15 minutes turn off.
Check your power supply. Looks like your power supply could not provide enough power for some reasons, e.g aging....etc.
Thanks for the answer , but when I reboot on safe mode I got no problem, and my power supply is 650 watts.
are you able to unplug some case fans, dvd drivers, and anything else non-essential? if so, try that and see if it still does it. that should reduce the load on your power supply. Safe mode may work simply because the hardware isn't utilised to its full potentiial (good example is the graphics card in safe mode). If you overclock, disable the overclock lol! it could be the new case has a different airflow over the ram (for example), and thus now the ram is hotter and you need to use slightly less tight timings. Just one example! Run chkdsk on all your drives (maybe even thorough scan), update your drivers, see what happens then
I have an old laptop that does something similar although not that frequently, on mine it is the graphics card driver is an XP one as I could not fine one for Vista let alone Windows 7.
have you checked your power settings in control panal , by default if you are not using your pc for a certain amount of time your monitor will turn off and a little later the harddrives . check your settings ,then get some software to monitor your cpu and system temps . if its happening during a time when your not using the PC its probably a wrong power setting ,but if it happens during use ,it could be either power supply (failing) or not up to the job .or overheating.