I have a Dell desktop with XP and SP2.  About 2 weeks ago my browser (Firefox) began freezing up everything on my desktop anywhere from 1 to 15 minutes after turning on my computer.  The mouse and keyboard worked but I couldn't do anything with them because the screen was frozen, not even Ctl ATL Delete worked.. I would have to power off the tower.  IE was not doing this but I HATE IE.  I even tried Opera and like it as well as Firefox but I'm having the same issue of freezing up.   After several days of scouring Google everyone seemed to aim the problem at memory or hard drive issues, viruses, doing a registry CLEAN up, you name it.  Finally I came across a board that discussed it only happens with Firefox and Opera and it was narrowed down to sites with Flash player which I guess IE doesn't use.  After playing around a little I uninstalled Adobe Flash and the problem went away.  However, a lot of the sites I visit require Flash to make the site work or view the content.  I did a clean removal of Adobe Flash (the newest version) and then reinstalled the same newest version, same problem.. it freezes my browser.  Why would it have worked all this time and suddenly just started a few weeks ago?  I had not recently installed anything new so I thought it was strange.  My question is... I need to use something.. is there an alternative to Adobe Flash or is there something else I might TRY?  This is driving me crazy!Which version of Firefox are you running?  You may need to uninstall Flash using Adobe's removal tool.  You can get that here: http://is.gd/1Gd9NI believe it was 3.5 ( I had uninstalled then reinstalled the newest version from the Mozilla website and then unistalled it again and currently am using Opera).  Also, I had already uninstalled Adobe flash using the Adobe uninstall tool about 3 days ago and have had no problems with any browser since, however, when I play vids on my computer using any player type (GOM, RealPlayer, WMP, etc...) that my computer still freezes after a few minutes of play.  So... I'm thinking it's something in my operating system and I'm considering a reinstall of XP.  UGH!  I wonder whether hardware issues might be a factor here.  Do you know what temperature your PROCESSOR normally runs at?  Do you have any temperature monitoring software installed?  If not, you might try SpeedFan.

How old is your power supply and what are the wattage and voltage specs on it?  Have you made any hardware changes recently? My computer is 1 year old..  a Dell Vostro 400 series.  I made sure both fans were working properly because I had seen other posts mentioning to check that, then I ran a temp scan and it came in normal.  No hardware or software had been installed just prior to the problem which started about 2 weeks ago.