This is the latest OS from Microsoft in 2007 right ?

I really really can't believe what users have to do for such a damn simple and very common problem. Who did design this ? Are they only living in the 1 disk for everything world ?
Doesn't it make perfect sense to choose on the installation how many partitions I want and getting one purely for the OS and a second one where I have all my data ? Do they really want all the users data on the C: ?