I recently used BootCamp (comes with the Mac) to install Windows 7 (have to buy it) on my iMac, so that my daughter could play Guild Wars.
I was pretty apprehensive, but it went well. First I cleared as much disc space as I could (overdue!), got about 100GB and assigned 60GB to Windows. Print out the instructions and follow CAREFULLY. It took a while but worked. Only trouble I had was installing the drivers once Windows was actually installed. It refused to run whatever it was, but I googled it and found a way to do it via command line and everything was fine. Pretty pleased with it TBH. (I’m a lifelong Mac user so still use that, but the Windows seems to be doing fine so far.)