Solved this with the expert help from  Dell!
I have a HP LaserJet P2015dn installed in Windows 7.  I have an older program that needs to run in XP mode.  I have tried all sorts of things, including Microsoft Answers, web searches and Protonic.com without resolving this.  It is clear that XP needs to share the printer installed on Windows 7.  I have gotten suggestions/answers that show what I have to do, but those do not correspond to what I see on my computer screen.  For example, "From the virtual machine window, click USB and then Attach (printer name).    I start Windows Virtual PC and find only "desktop,ini" and "Windows XP mode,"   I am in way over my head but this program is the reason I purchased Windows 7 professional.  I have the program loaded (along with 100+ data files) but I cannot print from XP mode.   Thanks.   Hugh Humphreys
sharing a printer between Windows 7 and XP mode