New to RD Tabs - so far, so good.
Is there a way to configure the software so when I connect to a remoter computer, I do not have to logoff the current user before I can take control of the computer?

If the remote machine is XP: Sadly, the answer is no. Microsoft allows only one active user session under Windows XP, so the local user must log off before a remote desktop user can log on (unless it is the same user, in which case the XP user only needs to lock his/her computer). The only exception is if you are doing an assisted session (Remote Assistance) which RD Tabs does not support. For that scenario, use XP's built-in Remote Assistance feature.

If the remote machine is Vista: The user simply needs to lock their computer, then the console will be freed and a remote user can log on. Vista supports concurrent logons quite well, even under a domain, but due to licensing restrictions, only one can be "active." That's why you have to lock your computer. If you want to share a desktop, again, look into the Remote Assistance feature of Vista.

If the remote machine is Server 2003: Admin Mode supports two concurrent logons plus the console session, for a total of three concurrent logons. If you go over that amount (or if more than one user attempts to user the console session), one will have to log off.

If the remote machine is Server 2008: Admin Mode supports two concurrent logons (no console session is available under 2008). More than two admins requires somebody to log off.

These restrictions are not a part of RD Tabs, but are a part of the Remote Desktop server. For more (assuming you have the appropriate licenses) concurrent connections, run Server 2003/2008 in Terminal Server mode.

That's what I thought but thanks for you time and help.