Windows Messenger 4.0 or Later on a Windows XP Professional
1) Click Start, click Run, type gpedit.msc, and then press ENTER
2) Double-click the following items to expand them:
Local Computer Policy
Computer Configuration
Administrative Templates
Windows Components
Windows Messenger
3) Double-click on the option "Do not allow Windows Messenger to run", and then click Enabled.
4) Click OK, and then close the window