Just thought i share yet another tips i experience and solved it with the help of mr google..
I setup a Windows & Pro PC and trying to use the Windows Virtual PC everything went on smoothly except for thatafter i install SQL Server 7.0 in Windows XP Mode, the XP Mode asked for a password for user XPMUser whereas i never specified any password before.
After some searching i found the solution from another forum...
specifically try to find the below entry by Mr Eli Sand
i followed it and solved my issue with. Pretty easy once you know how to do it :o)