Bear's right, just leave them alone. If you really want, you can move them to another disk/partition to keep defragmenting to a minimun (some say that putting them on another disk speeds performance, it hasn't made too much different on my system). You cannot change how much space swapfiles use, but you can change the location of them.
Here's the short, sweet answer. If you don't want swap files, go buy a lot more RAM. Swap files are used only when there's not enough physical RAM to handle everything. The performance loss comes from simply using swap files, not having them on your disk later--
deleting them may actually cause performance problems, as the system has to run through the commands used to create the files every time you delete them. And if the swapfiles are being used even a tiny bit, you won't know it, and deleting them could cause some massive problems in any programs running--
pnw