I got this from the PimpRig forums

Posted by: TekXoID

To disable ToolTips in Windows XP:

1) Open the Registry Editor
2) Navigate to HKEY_USERS\.DEFAULT\Control Panel\Desktop.
3) Double-click UserPreferencemask and change its value to 3E 00 00 00.
4) Close the Registry Editor and restart Windows.
Hope this helps ya.

Corn

<edit>I just found this at ActiveWindows:
To enable it again, change the value back to BE 00 00 00
</edit>