PC shuts down while running Windows

1st ur desktop is too old to run windows 7 since ur hardware is not compatible
2nd u must reinstall ur windows xp operating system and then head to the hp website and download the drivers responsible to run ur system normally http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?product=90862&lc=en&cc=us&dlc=en&lang=en&cc=us

Just do a Google search for windows xp disc and you'll get results similar to this

http://www.google.co.uk/products/catalog?q=windows+xp+disc&oe=utf-8&rls=org.mozilla:en-GB:official&client=firefox-a&um=1&ie=UTF-8&cid=11969216369837725015&ei=VE5LTMLoMZn40wSCr6CFCw&sa=X&oi=product_catalog_result&ct=result&resnum=3&ved=0CDgQ8wIwAg#

You can try to do a Power drain of the system ie disconnect all the cables from the pc and press and hold the power button of the tower for 30 to 40 sec. than reconnect only the keyboard the mouse and the monitor and turn it on. try to enter the BIOS page ( keep on tabbing the F10 key to enter BIOS is Windows Vista during the start up and F1 in Windows XP) and from their you can run a Smart test on the Hard drive. You can also try to boot the Pc to the safe mode and check whether the windows loads or not. From the Advanced boot option try to do a Start up repair.

Uninstall SP3. In certain cases improper installation of sp3 has caused the system to slow down.

try firefox! www.firefox.com, way better than IE

If you can boot into safe mode, then once in safe mode open system restore and then restore to a couple days prior to the install of the hp drivers. This should fix the problem. If you need to know how to get into system restore let me know your operating system (Vista or XP)

Firstly Remove SP3 through
http://support.microsoft.com/kb/950249

Then Download SP2, it works fine. Either way u can also go for SP3
Then try again for IE* or Mozilla

Hope It Works Out ur Problem

try running ccleaner

http://www.filehippo.com/download_ccleaner/download/86e6a458e780243c3a944b66ec60b319/

you can junk the IE for an extremely popular browser called Mozilla Firefox. Next time IE is up and running download firefox at :
http://www.mozilla.com/en-US/firefox/ look for the DOWNLOAD button.
you will be asking yourself "why haven't I done this long ago?"
Don't forget to rate me fixya!
thanks

Both of your browsers may be conflicting with one another until one is sucessful.Try to disable firefox and only have i.e. If this clears your problem than you need to chose which one you want.Let me know.