It can't be running at 27RPM, no hard drive spins that slow. The slowest speeds are in the thousands of RPM. It's probably either a 5400RPM drive, or a four thousand something RPM drive, or maybe an even slower one, but it's much higher than 27RPM.
There isn't much that you can do to speed it up significantly. You can avoid filling it up too much, keep it de-fragmented, don't have excessively large page files and if possible, disable the page file (only if you have enough RAM, I'd suggest 8GB before doing this), make sure that it has it's I/O caching enabled, and not much else. You can't change the RPM of a hard drive (at least, I've never heard of it being possible at all), so there's not much that can be done to make older drives able to compare to newer drives.