In Windows Server 2003 you could have multiple Remote Desktop session with the same user. In Windows Server 2008 this is not possible by default. If you login with the same user account the first session will be taken over by second session.
But you can allow multiple Remote Desktop sessions per user by changing a registry key.
- Start regedit
- Check out the follwoing registry key
- If the fSingleSessionPerUser value doesn’t exist, create a new DWORD value named fSingleSessionPerUser
- Open the fSingleSessionPerUser value. The possible values for this setting are as follows:
0x0 Allow multiple sessions per user
0x1 Force each user to a single session
- save this
Found this on remotedesktoprdp.com