How to get rid of them
If you detect viruses in your files they should be deleted and replaced with the original clean version.
If it is a 'Boot Sector or Partition Virus' then use a virus removal program
(viruses at essex.ac.uk)
For all virus removal you should boot from a "clean disk" with the write protection on.
This will help prevent the spread of the virus to the disk and your computer being infected again.