I need to run a x64 version of Windows in order to run SharePoint 2010.
- Can I run this on a machine that is running a x32 bit version of Windows?
- Can I run this on a machine that has a x32 bit CPU?
It strongly depends on the virtualization platform you want to use.
With VMWare, you can run a x64 guest on a x86 operating system, provided you have a x64 CPU and it supports Intel VT extensions (or their AMD equivalent).
There's no way (I know of) you can run a x64 system, be it guest or host, if you don't have an actual x64 CPU.
You specifically mentioned Microsoft Virtual PC, which doesn't support 64-bit guests at all, regardless of whether the host is 32- or 64-bit. As the other person answered, you'll want VMWare for this.