One thing you might want to consider: WinXP allows for defining a strict rule for installing/uninstalling applications. Just make sure installing/uninstalling rights are given to you specifically - and the problem is gone
On a sidenote: yes, MTW leaves savegames undeleted. I had to uninstall my MTW last night because it started freezing for no apparent reason (the recent attack of frost in Poland must have had something to do with it, apparently), but my two current saves (including my new Expert Early French GA campaign) were there . I promptly made a backup, just in case they get mysteriously overwritten during a re-install...