disables antivirus

CCleaner for Windows CCleaner Windows Bug Reporting
1

:angry: I had to re-install my OS (Windows XP Prof. SP2) and all apps and data due to a hard drive problem. The last thing I installed was CCleaner. After I install a program I always restart my system before I use the program or continue installing other apps. After I installed CCleaner and restarted my system, my antivirus program was disabled! I'm using BitDefender 10. Prior to to installing CCleaner, I'd installed several other programs with no effect whatsoever on my antivirus program. I can only conclude that CCleaner did this. I un-installed CCleaner immediately and will not use it again.

2

It's highly unlikely that CCleaner caused you any grief such as trashing your system, and was most likely something else.

Also you could have given the built in Windows recovery tools a try before formatting and reinstalling and those would be:

Last known Good Configuration, and System Restore.

3

If you just installed CCleaner and rebooted then there is no way it could have disabled bitdefender.(even if you ran CCleaner is shouldn't have been able to delete bitdefender. Unless you installed it in a temp file or something.)