Just FYI: you can run Windows XP Mode on Linux, under Virtualbox. The installer file for XP Mode is a zip archive, which contains a CAB archive, which in turn contains a VHD file that Virtualbox can use. Obviously you need a license string to use it for more than 30 days, have access to Genuine Windows features, etc. Virtualized XP is amazing on a multicore 64-bit workstation, BTW. It launches in about 3 seconds, and is snappier than native XP on a slower machine. Almost less like an OS now, and more like a program for running legacy applications.
Not really Xp mode which is specific to Windows 7 but a VM based on the Xp mode base VHD. I've created several VMs from that image which has SP3 nicely slipstreamed. It will activate with any unused Xp product key. Activation is suppressed in Windows 7 Xp mode. I tried it but found it needed to be run in administrator mode to work right and that was a no go in a Windows 7 system that is run in user mode. There were some tweaks to limit privilege. The file permissions the Xp mode VM saw were different from the native permissions but I still didn't trust it. It was way too integrated into the Windows 7 environment. I prefer my VMs to be tightly contained in their box. I went back to Virtual PC 2007 which doesn't blur the boundary between host and VM. Xp is nice in VMs due to its relatively low resource usage. I have both Virtualbox and Virtual PC 2007 Xp Vms running in Windows 7.
The newer version of Virtual PC. I tried it with a non XP mode XP VM but it was still difficult to navigate and the only benefit was USB support. I went back to the cleaner and simpler VPC 2007 which is pretty much the Connectix version with a a few tweaks. Simplicity is its virtue. Virtualbox does a much better job at more complex VMs with more virtual hardware options.