Technically:
it would be possible to buy the bare bones VPC which, when run, would give the impression of being a DOS based machine. C:>, etc.
At that point you would be able to install your copy of Windows XP Home and it would work. You will still have to register XP or it will shut down in 30 days.


Morally:
The tricky part here is that this is almost certainly illegal and you will still have to register XP or it will shut down in 30 days. Registering is not a problem as long as the XP you are using has not been "borrowed" and has not been registered before. Unfortunately, your copy will NOT meet those criteria.

Best, and safest, solution:
Buy the version of VPC with XP included, and feel good about yourself.

Question:
Do you have something special you want to do in Windows? Something that you cannot possibly do with your Mac? I note that you have not given any details about your machine and this plays a very important part in running VPC.

P