Cheapest solution would be to find a used laptop loaded with XP and call it good.
When my personal home PC died, I had many programs that did not play nice with regular Win 7 and I was considering the same thing you are now--buying a new, expensive computer with Windows 7 pro and hope it works.
Long story short, I went to a local used computer store (along with a coupon I downloaded off his Craigslist ad) with my old hard drive in hand. The guy showed me several computers, I picked one, he installed my hard drive as a slave, checked the install (worked great), and I paid him my $108, and I was out the door in less than 5 minutes!
I still am a happy camper 6 months later.
These places have laptops too.