if you havent been creating backups yourself and you are using the master recovery discs supplied with your system you will lose everything since you owned it as master recovery discs basically do a clean install, if you are using your own created discs you will lose everything from when they were created ,the sasser worm can be removed if your system will run , take a look at www.symantec.com for sasser worm removal tools which are a free download and cover all variants