Okay guys i had the same problem as some of you. I wanted to uninsall windows live beta so i went to control panel and did it the obvious way. Later i decided i'd made a hasty decision and wanted it back. So i went back to the site i downloaded it on and it didn't work. it said i still had it even though i swore i uninstalled it. Zapmessenger also didn't work for me and neither did those Run codes because the file i had deleted couldn't be found.
Finally after days of searching for the right solution i discovered a site and downloaded a program called Windows Install Clean Up which can be downloaded here: http://support.microsoft.com/kb/290301
This is completely safe, no viruses or anything if that's what some of you are worried about.
After it's downloaded go to Start, All Programs, look for Windows Install Clean Up. A box will come up with a list of every thing you have on your computer. Scroll down the list until you find Windows live Essentials, Windows live writer, Windows live Messenger and whatever else you want to get rid of. Select them one at a time and click delete. And that's it! you're done.
This works seriously so try it:)