Reading it over it seems he bought a new PC for work. It had W8. The tech put XP on overwriting W8. The OP has a PC at home. Instead of "wasting" the W8 he wants to install W8 on the home PC.

Seems like the solution, if his home PC has XP, is to buy a new PC at work, leave the W8 on it. Bring the home PC to work, and run the existing XP on that after installing any required programs like MS Word or whatever. Then bring the new PC home.

Ok, I'm kidding. But it would probably be easier to do it that way.