Install Windows on MacBook Pro using External Hard Drive

Hey y'all,
I am going to school for Systems and Networking Support and almost all of my studies are in Windows, but my main computer is a Late 2011 MacBook Pro, and I have a low end Windows XP, which is painfully slow, I use. However, I have a 1TB External Hard Drive, so instead of using Boot Camp, could I Install Windows on this External Drive and just boot from the External Drive when I want to run Windows?

Just curious, I could use Boot Camp, but using the External Drive seems more attractive to me.