I'm not sure what you are getting at.
You have two hard drives.
Two installs of XP.
When booting up, are you asked to choose which one to start? If so, then you have a "dual boot" system. Many people have this setup for testing software, gaming and so on.
They cannot both run together (at the same time) .
So it seems you have a problem with virtual memory. Try this:
Virtual Memory in Windows XP