It is easy. I installed windows XP then windows 7 to make a dual boot without problems, the drivers are a pain however win7 has them all, now to install Vista to upgrade to 7 is easy too don't know where the difficulty lies.
Installing windows = following instructions on the monitor :).
Remember that you can fail installing windows and nothing bad would happen, just try again and that's all. You will not break your drive just because you installed windows incorrectly :P.
Imagine if you would need to compile the code in windows' console before installing a new Windows version...
Mors Indecepta
Might controls everything, and without strength you cannot protect anything. Let alone yourself...