Caveat for Linux newbies:
Under no circumstances are you to choose the "beginner" installation. The reason: the beginner installation has two options, a 300 megabyte barebones install, and a 600 megabyte behemoth install. No middle ground. Not to mention, it installs GRUB/LILO on hda1, that is to say, it overwrites the bootloader of whatever is on the first partition (usually windows). It does this without asking you, or telling you before it's too late. And it doesn't make a boot disk!
I would also reccomend that you avoid the "advanced" installation unless you are indeed "advanced." When Linux says advanced, it usually means it.
Update as of Mandrake 8.1: If you have installed or used Linux before, and/or if you don't have anything terribly important on the target computer, or if your curiosity outweighs the importance of said computer, then go ahead and choose the advanced installation in Mandrake.
When
Mandrake says advanced, it usually doesn't really mean it.
Disclaimer: Back up your fucking data. This is important. I am not responsible if you lose gigs upon gigs of mp3s and pr0n due to an unintentional partitioning/reformatting.