I've had the best luck with just using one big partition. It makes cloning the drive fairly easy when going to a new HD or creating a "live" backup drive, and I just park all my data in the "my documents" area so backing up everything I care about is as easy as dragging the my documents folder to the backup destination.
I used to partition everything according to the recommendations of the old unix gurus (typically 4 partitions for boot, applications, swap, and user data) but I never actually saw any tangible benefit of that when using a single drive. If you have multiple drives, then by all means tell windows to point "my documents" to the data drive, and consider moving your swap to another drive as well. But if you're on a single drive, one big partition seems to be as good of a solution as any. I have never had a hard drive failure that would have taken out only one partition on a drive... Either it's all good or it's all bad, and having multiple partitions was just something that took time to administer.
