Acer Aspire 5000 crashes intermittently-can't run any antivirus sc

Hi, I've got an Acer Aspire 5000. I'm running Windows XP 5.1 Build 2600 with Service Pack 3. I've had BitDefender 2008 installed for the last year (2008 worked fine or all scans, but computer crashed periodically). I'm on a home network with the firewall enabled. I upgraded to BitDefender 2009 and the crashes seem to increase. For the last month whenever I try to run a full, deep or quick scan, the fan winds up and then the laptop crashes after 2 minutes. I've read where the BitDefender AntiPhishing Toolbar caused Firefox to crash, so yesterday, I uninstalled BitDefender and downloaded Kaspersky trial version. Well, that didn't make it either. It crashed after 2 minutes. This morning I ran PC Optimizer, & ATF Cleaner & ERUNT. Then I tried to run Malwarebytes Anti Malware's quick scan. Heard the fan winding up and 2 minutes later it crashed. I'm very frustrated at this point, and I do have a Hijack Log created as well as a StartUp log. Can anyone help!? Thanks, Marilyn

Hi strout99, I suggest you post your HJT log in the correct forum to make sure your system is clear of Malware, then if you are still having problems the Malware fighter will advise you to post back here in this forum for further assistance. Good luck, Kind regards,