I made a file to remove the Sobig.f virus...
http://mirror.contribs.org/smeserver/contribs/btalcott/contrib/unsobigf.infSave it, right-click, and choose Install. The "default install" command is to delete the two files from the Windows directory and remove the Current User and Local Machine startup entries in the registry. If the virus is running, it won't be able to delete the files. Run taskmgr and end the "winppr32.exe" process beforehand, or reboot and use the .inf again (the first time should remove the autorun stuff so the virus won't run after rebooting).