multiple remote desktop in xp
1. Download ConcurrentRemoteDesk.rar download this files first
(http://www.ziddu.com/download/3630098/ConcurrentRemoteDesk.rar.html)
and extract the file (If you don’t have WinRAR click here to download). 
2. Restart the computer and boot in Safe Mode by pressing F8 during initial boot up and by selecting Safe Mode. (This step is only required if you’re currently running Windows Terminal Services or Remote Desktop service, and System File Protection has to be skipped and bypassed, else it will prompt error). 
3. Go to %windir%\System32 %windir%\System32\dllcacheand make a backup copy of termsrv.dll in both folders. 
4. Copy the downloaded termsrv.dll into %windir%\System32,%windir%\ServicePackFiles\i386 (if exist), %windir%\System32\dllcache 
5. Then run the downloaded Multiremotedesk.reg to merge the registry value into registry or you can add it manually
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Terminal Server\Licensing Core]
“EnableConcurrentSessions”=dword:00000001 
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
“EnableConcurrentSessions”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
“AllowMultipleTSSessions”=dword:00000001 
6. Click on Start Menu -> Run command and type gpedit.msc and press Enter to open up the Group Policy Editor. 
7. Navigate to Computer Configuration -> Administrative Templates -> Windows Components -> Terminal Services. 
8. Enable Limit Number of Connections and set the number of connections to 3 (or more). This setting will allow more than one users to use the computer. 
9. Ensure the Remote Desktop is enabled in System Properties -> Remote tab by selecting the radio button for Allow users to connect remotely to this computer. 
10. Enable and turn on Fast User Switching in Control Panel -> User Accounts -> Change the way users log on or off. 
11. Restart the computer normally. 
To uninstall, revert back to original termsrv.dll .You probably have to do it in Safe Mode if the Terminal Services is enabled and running.