Smaller partitions also improve performance because files load faster from smaller clusters, and also take up less space.
Always put your OS on a neat 10gb (or so) partition, and install programs on another, and documents on another - then when things go wrong you don't have to worry so much about reinstalling. Always install your PC as if you'll need to reinstall soon, like keep copies of all your drivers and installers on a storage drive to save messing about. Especially network card drivers - it can be tricky to get anything done without them.
I think you'll need to find a program like Partition Magic, Windows own partition stuff sucks and probably won't be able to help.
Van-B
Put those fiery biscuits away!