[Will]

Just about every desktop computer in the past several years has had the bottleneck at I/O instead of processing power. If you want a speedup, the way to get it is to reduce latency with I/O. From what you've said, I can think of two ways to do this:

1) Add more memory. Preferably the max your system allows. It takes microseconds to access data in memory, while it takes milliseconds to access data from disc. Maximizing memory allows you to cache more data in memory, which means you'll need to hit the slower discs less.

2) Split your discs. If you have four partitions on one disc, you still have the latency of one disc. And if you have the disc trying to access game data on disc while Windows is trying to access virtual memory, you got the read heads seeking all over the place on disc. Partitions are great for managing data and having a more modular approach to backup, but it doesn't do you any performance favors. Imaging your C: drive onto a new drive (10krpm helps) should help out a lot.