If your BIOS has been trashed, you caught something more serious than PrettyPark. All this thing does to your machine is change your registry so it uses a file called files32.vxd to open EXE files. By running that file, it can send itself to other people by email, and try to establish a connection to the author where he can get your ISP password and such. A virus detection program may delete the files32.vxd program. Then you can't open any EXEs, and your operating system is quite hosed. All you have to do is fix the registry. Easier said than done when you can't run any programs. I'll email you a text file. It contains the following 3 lines:

REGEDIT4

[HKEY_LOCAL_MACHINE\Software\CLASSES\exefile\shell\open\command]

@="\"%1\" %*"

Note that there must be a blank line between each of the text lines. Put this text in a file called undo.reg on a floppy disk, using an uninfected computer. Right-click Start on the infected computer, click open, find and douple-click undo.reg. You may have to start your computer in "safe mode" by holding down F8 while it boots up. Good luck.