Hi Russ,Yes you can Dual Boot Windows Xp alongside Windows 7 but why would you want too?
If its just to play around on the older OS,s then why not install them in a Virtual Machine?
VirtualBox is what i use.
Heres a guide on how to do it though if you really want to Dual boot,Beware though if not done right you could mess up your current install of 7.
http://www.howtogeek.com/howto/8790/dual-boot-your-pre-installed-windows-7-computer-with-xp/