need help with your PC shutting down or locking up?

After you turn on your puter, hold down the F8 key before windows starts to load. This will start Windows in safe mode. When safe mode is running left click once on START, then RUN. Type in "chkdsk /r" with no quotes. The "Backslash /r" is a switch which invokes "repair". This will run check disk and repair any bad clusters on the hard drive. Next click OK. Check disk will tell you can't run now but ask if you want to run next time the computer is started, Type Y for yes.
Click , Start "restart computer". Reboot.
After the reboot "chkdsk" will run all by itself. It will test the drive and fix bad clusters for you. It will produce a report, read fast. Next the computer will restart on it's own.
Next run Defrag, left click Start, Accessories, System tools, Disk Defragmenter.
Highlight (or left click once the drive you are defragmenting, in most cases that would be "C" drive. Then left click "analyze". Then left click "defragment.
Get a cup of tea and wait. Do not spill the tea on the keyboard.
After defrag is done you can left click view report, or left click close. The report will tell you any files that did not Defragment and where they are. When I get files that will not Defragment I always run CHKDSK again in safe mode, then run Defragment again, sometimes it gets them the second time, for some strange reason know only to GOD and Bill Gates.