Windows 7 on external drive/Windows discs

Is it possible to install Windows 7 on an external hard drive and use on my Mac? I really want to play some PC games on my Mac but would rather not partition my hard drive for Windows. I mean, if it comes to that I wouldn't have a big problem with it. Also, how is the compatibility on using PC game discs in Windows on the Mac? Will Windows recognize the Mac Super Drive? Really, I just want to have Windows on my Mac so I can install Lord of the Rings Online and play and I already have the discs (my PC is KIA). Thanks for any responses.