Different login usernames

[piltdown]

I have FoG for both PC and Mac which were setup with different user names. If I try to login using the credentials originally used on the Mac on the PC I get authentication issues and vice versa. What I want to do is to transfer the username associated with the Mac to the PC - is this possible. The main reason for doing so is that the Mac version is no longer being developed or having bugs dealt with.

How can I transfer the user name?

Thanks.