To update this thread, if you have Win 7 Pro or Ultimate, and have a full (legit) copy of Windows XP, Windows Virtual PC offers an easier configuration over VirtualBox. You don't need to create specially shared folders, don't have to install extension packs (for Intel hardware), and is more reliable. If you don't have a retail disc & COA, that's fine, XP Mode is freely available from the site.
Genuine Microsoft Windows 7 is required, your install must pass validation prior to the download.
Your external hardware is also easily attached, you just need to install it, just as in Windows 7, after installing guest additions. So when installing a printer or other hardware, remember to select XP SP2-3 (32 bit) as the software to download. Many modern printers will work with XP SP2 & up, but the software for the installer is different.
And if you have the choice, always enable hardware assisted virtualization (HAV) through the BIOS options. Instructions for various computers can be found on the Windows Virtual PC site.
http://www.microsoft.com/windows/virtual-pc/
To configure the BIOS for HAV:
http://www.microsoft.com/windows/virtual-pc/support/configure-bios.aspx
If you don't have HAV as an option, there is an update on the Home page of Windows Virtual PC to enable you to run it. It's the third update for those who needs it (Windows 6.1 KB977206 x64.msu). This is a standalone installer, there is also one for 32 bit OS's/systems. NOTE: This update is ONLY for Windows Virtual PC, it'll do VirtualBox & VM Ware Player/Workstation no good.
If you need to have a Linux VM, they don't work well with this setup. I've tried and tried, sought advice, it'll boot, then crash. If you need a Linux VM, then VirtualBox or VM Player is suggested. Same with Win 2K, it'll install, but guest additions aren't supported for it.
The latest versions for VirtualBox & VM Ware Player can be obtained at:
http://www.filehippo.com/
Through this route, no registration is necessary for VM Ware Player.
HAV should still be enabled in the BIOS, if the option is available to you.
Hope that this post is of assistance.
Cat