Hi Luciel,
When your Windows messes up the hard disk and you only have a single partition, you will lose _all_ your data: system, applications, games, movies, pictures, everything. Then you may think about if, perhaps, multiple partitions are a better choice.
Also, I don't quite understand what you mean my a multi-partition setup being slower. If you ask me, having the system and applications on one hard disk, and games, movues, pictures and the swap file on another hard disk is even better as it distributes load onto two hard disks rather than one. Also, you can make backups of files from one hard disk to the other (poor man's RAID

): if one hard disk fails, you still have the important files on the other.
So, I'm not only for a multi-partition but even for a multi-_hard disk_ solution. Damn, another off-topic post...!
Joe