HELP!! Windows Messenger Will Not Stay!

My problem is that I need Windows Messenger in order to
use the remote assistance with my mother who lives in
another state. The only way I can get access to
Messenger is to uninstall and re-install each time.
After shutting down the PC, messenger is not accessable
(it just sits and does nothing when I click on it), nor
is it in my system tray. I've read all the posts
regarding this type of problem and have added Messenger
to my startup group. I've made Windows Messenger my
default IM (after installing XP Service Pak #1) and have
done everything else suggested in this newsgroup. Any
suggestions??? (My son uses Yahoo and AOL Messenger on
occasion, would this affect Windows Messenger?? I also
use Outlook Express and have checked all necessary
options there as well).