PC Shuts Down by Itself and then Immediately Reboots

hi,did you checked with any antivirus.No virus it will be the computer motherboard problem,otherwise hard-disk problem.

Two days since I plugged it directly to the wall and disassembled everything out of the case then cleaned everything even though its not that dirty, the problem stopped. I thought that the problem was really fixed, but lately it happened again. I checked the comp and I saw this ants lined up and going inside again. I am not sure if these ants is the reason why this happens. Also, I dont think that I spilled something that might attract the ants to go inside, maybe they are just searching for a new nest. Lately, I discovered that some holes in my desktop table is actually a nest with eggs inside =). I will clean the comp again, relocate it and observe if it will work =). If it still happens I will take it to the technician.

By the way, when it reboots it is always saying that "windows did not shut down succesfully...etc." and asking me what to choose from safe mode, start windows normally, etc. What does it mean when this screen appears?

The error means it wasn't Shut Down correctly.

Boot the Win7 DVD or System Repair Disk to run a few diagnostic Startup Repairs.

it means the system is not shut down properly through normal windows shutdown option. this happens when the pc suddenly turned off by itself then reboot, it's the same as manually pushing the off button to force shutdown the pc. well, if possible you'd better choose last known good configuration.