The same thing happened to me - many times, before I found a solution. I have answered this question for many other people as well, but I guess it's hard for you to find the answers I left. Too bad you didn't search the Questions first.
Yahoo leaves many traces of itself in the registry when an old version is uninstalled or a new one fails to install properly - (my uninstall left close to 30 references). The new version will not install completely until they are cleaned out, but you can leave in your profile for Message History if you prefer. (I hope you 'saved' Messenger instead of 'run') I spent hours reading for solutions before I came to the only method that works, and it requires deleting all Yahoo Messenger references from the registry. (Be very careful - you could make a mess there!) File Hippo has several versions of Yahoo Messenger.
Use a search engine to find Lenny Vasbinder's column on 'How I ALWAYS Do a Clean Install Of Yahoo Messenger on XP'. He has a blog too, but I had looked for info on installing Yahoo Messenger - I think the reference was not even on the first page of results - lots of reading first ... It should also work for Vista and Maybe Win 7, but I don't have those. It does take a lot of time, but should be worth it. I had tried Yahoo Support Desk too, but it didn't cure my woes, alas.
Take the time - hope it works for you too.
http://www.filehippo.com (several versions of Yahoo Messenger program)
http://www.winaso.com/ (only deletes 10 at a time in trial version, so needs to be run several times)
http://groups.yahoo.com/group/Yahoo_Messenger (you have to join the site to search it)
Lenny Vasbinder's blog or the title of the article itself, in quotes, in a search engine
· 10 years ago