COMPUTER WONT BOOT INTO XP

My computer will not completely boot up. It gets as far as the login screen with the user names, but when I click on any user name it just reboots automaticcaly. Will not boot in safe mode either. I am running on a bootable cd right now (bart pe) so I can access the internet for your help. I believe it to be caused by a virus, as my anti-virus software (Charter high speed security) was quite frequently finding viruses but unable to remove them. I ran a bootable cd (kaspersky) anti virus and it found and removed some things, but still was unable to boot up from my hard drive. I even tried running recover from my set up disk, but it asked for an admin password, and I don't remember ever putting one on. Any help or ideas would be greatly appreciated. Thanks, Tim

Please download the current version of HijackThis from HERE

• Double click and run the installer.
  
• It will install to C:\Program Files\Trend Micro\HijackThis\hijackthis.exe
  
• After installing, you should get the user agreement, press accept and Hijack This will run.
  
• Select Do a system scan and save a log file. This will open a notepad file of everything Hijack This found, copy and paste it back here.