Restoring the OS and the Trojans in the boot files

Hi

I’m just a pc user and I’m new to this software. My XP backup is stored on the separate partition. It was created with the “True Image 11”. I haven’t initially created the “boot CD” so it is unavailable for the recovery process.

The system was severely infected with the viruses/trojans. My question is:
Would restoring the OS from the backup wipe out the Trojans in the boot files or do I have to totally reinstall XP to get rid of the infection?
Thank you.