Another installation is in progress

Solution 1:

Go grab the Process Explorer from Sysinternals.

You should be able to see the msiexec.exe service running, and if something is in the middle of installing you should see other msiexec.exe children processes. It would be best to allow them to finish, and maybe try to squeak your install in between.

I have seen it before where the .NET Runtime Optimization Service is constantly firing off ngen.exe using the installer service to generate optimized .net assemblies and never allows the installer to use anything else. You can try stopping that service to see if it makes a difference.

Solution 2:

Have you checked for malware?

The Windows intaller service is normally set to manual and the buttons will be greyed until you change to Automatic.

Two instances of MSIEXEC running seems unusual. do you have AV software running? Is it up to date?

Anything unusual in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\run ?