I've been looking thru a bunch of threads and it seems that people don't realize you can run multiple instances of D3 on a single PC. Although this way takes up twice as much space, it is more efficient then having two computers. All you need to do is copy the D3 folder and have two shortcuts each pointing to one of the client. Also in the shortcut property you need to add '-launch' to the end of the target file.
Hopefully this helps people trying to run the ZK exploit scripts(my script just alt+tabs between the clients) or just multiboxing easier.
Edit: Also people have been complaining that when they run multiple clients using only one instance of D3 files, that it is really slow. My speculation is that because Blizzard loads their resources dynamically the second client gets hung up waiting for the first client to load.