Try to first download and install a new copy from Microsoft.
If that does not work then you will have to remove the old copy and then install the new version.
You risk losing all your old contacts though.
- Go to 'control panel'
- then 'add/remove program'
- remove 'msn' and 'messenger'
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix instant messaging.