I can't change the install directory for Yahoo Messenger or launch it once it's installed in the default.

My Yahoo Messenger stopped working--I could not authenticate--last week. I uninstalled and tried to reinstall. When I tried to reinstall Yahoo Messenger, changing the directory caused the install to abort. If I leave the directory the same, I can install, but the program will not launch. I have deleted the Yahoo directories in the registry (both hkey_local_machine/software and hkey_current_user software) before installing with no luck. I've tried with the latest version as well as the version that was available in February 2007.I can't change the install directory for Yahoo Messenger or launch it once it's installed in the default.Email customer care they can help