Not sure comments like that are appropriate (logicearth) -- the OP said that his legacy application NEEDS this type of stuff and it's currently too expensive or not practicable to either install a new application (would need to train staff and possibly change the business process in the organisation).
It's very EASY for an individual to go out and say "Ditch the old app -- I'll go and install a new one) --but businesses aren't like that -- some have systems still running that are 40 years old or even older. I can name at least 7 instances where some old IBM Mainframe COBOL is still being used daily.
Most businesses don't have any interest in the computers --they just want the applications to run -- usually as cheaply as possible.
I'm quite sure if the business thought it was worthwhile to change the application plans would already be in hand to do it.
I'd go about it this way
1) forget Virtual PC and XP mode -- run a fully blown XP virtual machine on say vmware player or vbox -- both FREE . Install your Dbase software on the XP VM.
2) Now you CAN share printers between XP and Windows 7 (32 / 64 bit mix) -- I posted a thread on how to do this on these Forums.
Read my post (nr 3 ) in THIS thread Networking from Printer attached to Win XP PC to Win 7
Problem solved !!!!