Windows 7 Virtual PC supports Windows 7 XP Mode that provides facilities to run Windows XP under Windows 7.
This copy of XP runs in a Virtual PC supported by Hardware Virtualization feature of the processor. You can run XP programs and use XP only devices like printers and scanners in this XP-Mode. This allows you to use your old peripherals that are not supported under Windows 7.
The hard disks on the machine are shared between Windows 7 and the XP-Mode programs. Devices attached via USB ports can be used in either program one at a time.
You can read more about this mode
I have installed this feature on my machine to mainly use my HP 1010 Laserjet printer and HP 3010 Scanjet scanner that are not supported by Windows 7.
Both are attached via a USB port and work very well in this mode.