They can both have the same user name.
To have them run in the background, run them as a "service". I believe you do that when you install it by selecting "install as a service" but I forget the exact wording. There's probably a way to make an existing program run as a service (since you already have it installed) and you can see your services in Windows XP by right-clicking on "My Computer" and selecting "Manage", then in the pop-up window selecting "Services and Applications."
It's also recommended that you use the "local" flag when running two instances of folding. I do it by creating a shortcut to the folding application, and in the "target" field typing in " -local" at the end of the text. The space before the "-" is important, I think.
It looks like this:
"H:\Program Files\FaHConsole1\FAH504-Console.exe" -local
I'm not sure how to run it as a service and run the local flag at the same time. I'm also not sure how critical the local flag is, but it's one of those things that "everybody does."
