My nieces  CPU , she thinks she got a virus. She uses AVG. Here what her CPU is doing. When she turns it on it loads up to her desktop then shuts down. I had her try it in safe mode and it does the same thing. She TOOK it to a COMP place and they said they would have to get her save pics...etc..off then put a new OS back on it. What I was wondering is how can you get her pics and etc off if you can't get the comp to boot up and stay on. If I vcan get here stuff off of the comp I can put a OS back on it. She is running WinXP.. Thanks..this is my first message on this Cpu forum, hope I put this in the right place Welcome to CH.
Just leave the computer off for awhile. After ten minutes turn it back on and try to get into the safe mode. This is done by tapping the F8 key before Windows starts.

Is this a laptop and is the BATTERY well charged? A WEAK or defective battery can make the laptop restart.
If this is a Desktop, what SUB devices do you have? So devices dares to much poser and cause the desktop to restart.

Another POSSIBILITY is that the fan my be stuck or broken. A Desktop PC has two fans that must cool the processor and the power supply.If the computer gets to hot is restarts or shuts off.

Do you have an Anti-Virus program? Did it indicate a problem?It's a desktop , and yes  they are using AVG. and it did show several virus. I haven't look at the cpu myself but she going to bring it over so I can look at it. I'll do what you said in the reply and check it out. Thanks for the reply. I'll get back. I headed for work this evening. Thanks again.