Windows XP Mode and Windows Virtual PC, available on Windows 7 Professional and Windows 7 Ultimate, allow you to run multiple Windows environments, such as Windows XP Mode, from your Windows 7 desktop. If you are not currently running Windows 7 Professional, Windows 7 Enterprise, or Windows 7 Ultimate, there is an easy upgrade path to Windows 7 Professional or Windows 7 Ultimate through the Windows Anytime Upgrade program.
Depending on the type of physical connection the scanner requires (USB or Parallel) you may be able to install and configure the scanner within a virtual environment via a direct USB connection or through attaching a USB to Parallel adapter to Windows XP Mode as a method to bypass the lack of LPT redirection in Windows Virtual PC.
Windows Virtual PC can emulate some hardware devices, but cannot access the physical hardware devices on the computer directly. In many cases, USB devices in Windows Virtual PC can be used. Windows Virtual PC uses the Redirection Policy Manager (RPM) of Windows to provide USB redirection to a Virtual Machine; HID and Hub Class Devices (LPT and COM ports) cannot be assigned to the VM. So presuming that the connection made from the scanner to the Windows 7 PC is via USB you just might be able to install and configure the scanner through Windows XP Mode.