So my computer is randomly rebooting. No windows shutting down screen, just turns off.
Power supply? Motherboard?
I just swapped hard drives so its not a virus.
What do you think?
right click on “my computer”, click manage, right click Computer management(local) then properties, click on the advance tab, click settings under start up and recovery, unselect the “automatically restart” check box under system failure. Now when ever it restarts it should halt and give a blue screen that will tell you the problem and if you need write it down and look up the conflict on google.
unless it’s rebooting because of a hardware error, which is probably the case considering…
ebay. buy a mac 
it’s probably bad RAM or motherboard but it could also be PSU, do you have a UPS?
My computer was doing the same thing. Pull the processor fan and get all of the caked dust out of the heat sink. You won’t believe what is in there, especially if used in a carpeted room.
Or just buy a Mac. That is my next move computer-wise.
while you’RE out buying a new mac like everyone is suggesting, get me one too.
Good idea if it stays on for a while then reboots (and for general maintenance), but not so good if the computer is “cold” and still restarts.
1.)Memory
2.)PSU
3.)MB
In order of easiness to check. (hardware wise)
P.S. if you get a blue screen look for the hex codes in the format 0x00000000
should give you a clue.
Also check the CPU/MB temps.
haha i have a strange problem with one of my comps, it doesn’t like to run when cold lol
it will reboot about 3 times, then startup just fine and be 100% stable lol
measure the psu rails with a multimeter. If something is dipping too low, it will cut the power.
Also could be a temp issue.
Get a copy of the ultimate boot livecd, and run the bootable mem test, then run a stress test for a few hours.
Was the extra memory stick i added a year ago…wish i knew that before i reinstalled windows…