Hi garby. To me the main advantage of partitioning is that if you have your operating system and programs om one partition, and all your saved files on a secon one, then if your Windows ever gets corrupted beyond repair you can reformat the primary partition without losing any of your important files. If you are using Outlook Express for your emails you can even set your Store Folder to be on the second partition. I have also set a third partition for a backup of the primary partition so I can restore the installation even more easily. Not as good as backing up to an external drive, but better than no backups at all.
Minuses. I cant think of any except installers usually assume your CD drive is D:, so you sometimes have to correct this to E: or F:. I have set my CD drives to Y: and Z: anyway.