The XP Mode and Virtual machine download is at:
Download Windows XP Mode
It's only available on W7 Pro, Enterprise and Ultimate. I don't know what happens if you lie on the download page and try downloading and installing it anyway - suspect it spots you have the wrong version of W7.
I use it for a couple of bits of ark-ware that won't work with W7, or possibly W7-64, and it seems to work well.
Another way round might be to use Sun's Virtual Box and Windows 2000, which doesn't check up in the same way later versions do.
PS I take it you've checked and there isn't a later version of your software you could download...