After upgrading your operating system to Windows XP, the PS/2 mouse only works in Safe Mode.

To correct this behavior:

01. Shutdown and restart Windows XP.

02. Press F8 on the Startup menu.

03. Turn off NUM LOCK and use the arrow keys to select a Safe Mode option.

04. Press Enter.

05. Start / Run / sysdm.cpl / OK.

06. Select the Hardware tab in the System Properties dialog.

07. Press Device Manager.

08. Expand Mice and other pointing devices.

09. Select the <PS/2 Compatible Mouse>.

10. On the Action menu, press Properties.

11. Select the Advanced Settings tab.

12. Clear the Fast Initialization box and press OK.

13. Shutdown and restart Windows XP normally.