I run windows xp and I am looking to increase performence. I have already replaced the shell "explorer.exe" with "cmd.exe" and am looking to further increase my system's efficency. What system processes can I terminate and what system processes can I assign low memory priority?

Get more ram! Or update your processor. Lowering the priority of certain processes won't do much.

Wow... you are getting into some really dangerous area's that can cause you much more trouble. First off you should be running between 26 to 35 processes when you first boot up. If you are running more than that go to Start, Run and type MSCONFIG. Go to the last tab on the Right and disable all startup items. then restart. Once this comes up go to Start, Control Panel, System. then click on the Advanced tab, Performance and click Settings. Then select the Advanced tab and select Virtual Memory. Then select "System Managed Size" and click Set. Then restart your computer. Once it comes up if the speed is not where you would like it to be then install more RAM, perform a Scan Disk and Defrag. That is as good as it gets.