deloy

I had to reinstall my OS (win XP) due virus, havent changed any hardware, and the OS is the same. Now i have dual OS, one which was screwed up because of virus and the newly installed one. However, as i had to reinstall BS again, I am being asked for activation, is it possible to avoid activation on new OS, as I havent really changed anything, just reinstall of the same OS? If this sorts out, I will delete the old OS Regards