Windows Messenger, older version issue.

Hi!

I have a newly installed Windows XP with the Windows Messenger that you can
presently download. I need to use the SIP services in my company which is
based on a older version of Windows Messenger. Thats not the problem though
since i managed to get my hands on the messenger.msi that i need (0680).

The problem is that i need to get rid of the new version to install the old
one. No matter what tweaks i've tried, spent alot of hours today googl''ing
and have gotten all kinds of tips. Like editing sysoc.inf to allow it to be
visible from add/remove programs. Do the RunDll trick to get it uninstalled.

But no matter what i do i allways get the same issue that it cant install my
old version since a new version of Windows Messenger is allready installed.

Please is there a fix that is actually working for something like this?

Big thanks in advance if you know the answer.