System Requirements for Virtual PC:
Windows Virtual PC - Wikipedia, the free encyclopedia
There are 2 types of Hypervisors, or methods of virtualization - one runs on software and the other runs on the hardware. See: Hypervisor - Wikipedia, the free encyclopedia
Perhaps you simply need to enable it in your BIOS? Looking up AMD 4400+ i see 2 models do and 2 don't have virtualization:
Compare AMD Processors for Desktops: AMD Phenom?, AMD Athlon? FX, AMD Athlon? X2 Dual-Core, AMD Athlon?, and AMD Sempron? Processor
Go in the BIOS and check.