Multiple connections to a server or shared resource by the same user, using more than one user name, are not allowed.

I was removing WinXP clients from a domain and then joining them to a newone the other day and came across this error:

Multiple connections to a server or shared resource by the same user, using more than one user name, are not allowed. Disconnect all previous connections to the server or shared resource and try again.

My leaving the domain was fine, it was the joining the domain that was the problem. However I had failed to read the message, I still had mapped drives to the shared folders on the old domain with the same user nameand folders. So I quickly disconnected the shares and the joining to the domain was instant!! I could then remap them all again.

Moral of the story: READ THE ERROR MESSAGE!!! They sometimes make sense :)