VMLite XP Mode is a free equivalent to Windows 7 XP Mode, that allows you to create and install a virtual version of Windows XP on your Windows 2000, XP, Vista or Windows 7 system.
If you've moved to Windows 7 and find some of your old software doesn't work, then, you may be able to get it running via VMLite XP Mode. You could do much the same with Windows 7's own XP Mode, but VMLite claim their version is significantly faster, and has many other great features.
VMLite XP Mode is generally easy to set up, for instance - a simple wizard walks you through the process. It can even download the XP image for you, although this might take a while (it's about 470MB, and installation seemingly takes forever).
Your virtual XP machine can share your internet and network connections, printers, even USB devices, making it quick and convenient to use.
There's clipboard sharing, too. Copy a lengthy password to the clipboard in the host PC, and you'll be able to directly paste it from your virtual XP machine.
And there's even the ability to take snapshots of your virtual system state, and restore them later. So even if you installed malware or performed some disastrous system tweak on your virtual XP setup, you can just switch back to a previous snapshot and any damage will be done.