Deleted some Program Files folders???

[Zefir]

Hi,
Very strange thing happend to my IBM T43 windows xp sp 1 system.

After some system updates (software update), one of them was bios update, next I uninstalled intel wifi driver I discovered most of programs in Program Files were gone.

I checked whole C partion with undelete software (FreeUndelete) and i found that programs were deleted.

What could happend to my system and how to resolve this problem.

PS. Rather not virus, I have full windows, antivirus and firewall software update.