I am in desperate need of an antivirus program that will work on Windows XP X64, does anyone have any suggestions.

The 64 bit version of XP has not gotten many good reviews. You might consider going back to the 32 bit version until Vista is released.

I had a similar problem with a test bed machine and found that it is possible to run 32 bit in compatibility mode.
It turned out to be such a pain in the rear due to lack of 64 drivers I went back to XP Pro 32.

I do agree with Scott here, give up especially if it is a domain networked machine.
Printer drives are hell to find.