256 RAM SEEMS to be insufficient if u have many program running in background at same time..try close off a few when using WMP..or better solution is to upgrade ur RAM to 512 or more..
Better to use one of the memory vendors' memory configurators to select memory parts that are 100% guaranteed to work with your PC/motherboard. Otherwise there is always a risk of buying memory that looks like it should work but is actually incompatible. Check other threads for recommendations on where to look for memory online.