That sounds really strange that a virus has affected the Limesurvey files. I am not an expert, but Limesurvey has not one exe file or anything. Anyway.
It depens very much on what you have done so far to your system.
If you did not uninstall/reinstall the mysql server, then the databases should still be there. What you need to do is make a backup copy of the database first (phpmyadmin).
Then install limesurvey again, using the database that you had used before. If you install the same version as before, you should be able to use the same database and there should be no problem. However, should a problem occure, you still have your backup.
