Partitioning makes a lot of sense. It helps keep things more ordered.
Keeping your OS, multimedia files, games and apps on separate partitions will speed up the search for particular directories and files in the explorer. Having to drill down through one huge partition with hundreds of directories and subdirectories gets frustrating really fast.
It simplifies making backups. You can keep separate backups of each partition labeled by drive name, instead of backups labeled with what different apps and files are on them.
It speeds up defragging of the more important directories that you'd tend to defrag more often, like the one the OS is on.
I'd split the drive up into:
C: 10 GB's for OS
D: 30 GB's for apps and docs
E: 40 GB's for games
Basically, take 3 more GB's from apps and docs, and give it to OS so you have a little more breathing room there. Of course, you can always use Partition Magic to resize them at some future date if you find the space balance doesn't suit your needs.
I have a 120GB drive split as:
C: 10 GB - OS and Utility Apps
D: 10 GB - Internet Apps, Docs, and miscellaneous files
E: 10 GB - Productivity and Multimedia Apps
F: 10 GB - Games
G: 80 GB - MP3's and downloads
I have a second 40GB drive in one partition
H: 40 GB - WinXP pagefile, WinXP ASR backup files, and movies.