Although partitioning does not speed things up in itself, smart planning can improve things considerably.
1. Every file has a minimum size. Even with nothing in it, the system allocates a certain amount of space. The smaller the partition, the smaller that space is. If you have a lot of tiny files, you will get more on your hdd with smaller partitions.
2. People think that big files are a problem. A drive with 200 movies is easier to read than one with 200,000 images. My video partition takes about 5 secs for PerfectDisk to read. My working images partition, minutes.
3. File numbers make a difference, fragmentation a big difference. My two hdds have about 400,000 files each and they are not particularly slow. I can have up to 120,000 file ops a day which means defragging some partitions every week. If I don't the pc slows down. A few more files don't make the slightest difference.
4. By sensible partitioning you can minimize defragging. Put all your base files like movies and images in their own partition/s. If you just play them, the partition will almost never need defragging because playing is just accessing the files not modifying them. The files stay in exactly the same place on the hdd.
Use another partition/s for working on/editing files/temp files. It will see a lot of file ops and need regular defragging. However, you only have to defrag this partition not your zillion Gb of movies.
There are lots of ways to partition to suit your style. My partitions are:
System and Prog Files
Working Area
Video
Daily Backups and Temp Files
Long-term Backups
Paging
Starman*