If you are facing problems while installing Live Writer, Live Messenger 8.5, or Live Mail betas, in particular if the the Windows Live installer disappearing halfway through (after a Windows Vista UAC prompt if enabled), this may help.
- Close all Windows Live applications
- Navigate to C:\Program Files\Windows Live and delete the Installer folder
- Navigate to C:\ProgramData and delete both Windows Live Installer and WLInstaller directories if you have them.
- Reboot (important!)
- Reinstall the application you want to install
This may be an issue if you installed the leak Messenger build, as all Windows Live beta applications need to be the same language. See the Windows Live Installer FAQs for more details.
Windows XP: All steps are same, except the step 3 above. The replacement for step 3 goes like this:
Go to C:\Documents and Settings\All Users\Application Data instead of C:\ProgramData.
Source:→ LivesideMicrosoft, Windows Live, Installer, Windows Live Installer, Betas, Troubleshooting