Vista installation problem

[Nirad9er]

I tried installing vista through virtual pc and It wont let me install it because it says my cpu is not compatible with 64bit operation or something like that. I cant remember exactly what it said. I have a opteron 170 which is definitely 64bit but why would it say my cpu is not compatible. It was the x64 edition of vista. does virtual pc not deal with x64 operating systems?

Thanks