In addition to Kovid:
If the (old system) HARD DRIVE is still workable: Remove the drive (seek help if needed) and attach it to the new computer by either installing it inside (If a tower model) or get a USB drive caddy or (bare) HD cloning kit
and move your Library folder and configuration folders to the NEW system HD
DO NOT EVER ATTACH A DRIVE THAT HAS A VIRUS TO A GOOD SYSTEM without major precautions. (I use a Linux boot, then copy just the documents I know to be not infected)