Speed up Java applications running in Windows XP?

One thing you could try is checking the Java version you're running. If you're still on Java 5 you should upgrade to Java 6 because there are a lot of performance improvements in Java 6.

Besides that it's very hard to give good tips of improving performance as I've got no clue of where processor power is going to:

1. Garbage Collection: If the program has to limited heap space it will spent a lot of processor time in collecting unreferenced objects (garbage). Increasing the maximum heap space of the Java process might help out. Playing with GC settings might help to, but that's a bit more advanced.

2. Swapping: If there's not enough system memory available for the Java process, it will start swapping it of to disk. Once this starts happening performance will go down.

3. Calculations in game: Nothing you can do here. The calculations could be needed, or they could be the result of poorly written code. In both cases you can only hope for another version or start upgrading your system.

Would creating a RAM disk be a good alternative?

have a look at this;
http://www.cs.cmu.edu/~jch/java/speed.html