Error 0x80070643: Fatal error during installation

Cannot install Windows Live Messenger 9 or other Windows Live Applications.

If you are currently using Windows Live Messenger 8.5 or an older version, and when you try to upgrade it to the Windows Live Messenger 9 Wave 3 applications from http://download.live.com/ using the Live installer, you get an Error message at the end : 'These programs could not be installed'.

I suggest you try the following steps to redress the issue:

1) Uninstall Messenger Plus! in case you have installed it. Uninstall the current version of your WLM. Use CCleaner to clear residual registry entries.

2) Try to install it again using the Live installer. If you find that your green animation bar progresses up to a certain stage and then again reverses back, it means that the installation has again failed. You may or may not get an Error Code 0x80070643 at the end.
3) This may occur when the installers has insufficient privileges to modify a file or a folder.

4) Open Explorer and through Organize > Folder Options > View > Choose to show hidden and system files & folders.

5) Next navigate to
C:\ProgramData\Microsoft\IdentityCRL
and Take Ownership of this folder. Do so easily now with a single click ! Download this registry fix and just add it to the registry.
Add_Take_Ownership.zip This option will now appear in your Rt-Click.

You can add this command easily using Ultimate Windows Tweaker.

6) Try now. It should work !

Or try to go to Start>Run, type cmd with admin rights and then enter each of these one at a time at the command prompt (hit 'enter' after each one if needed):

regsvr32 wuapi.dll
regsvr32 wuaueng.dll
regsvr32 atl.dll
regsvr32 wucltui.dll
regsvr32 wups.dll

Also did you try the full installer http://g.live.com/1rebeta3/en/wlsetup-all.exe ? if not try install in Safe Mode