The 2203 error code literally means “Cannot open database file”. One of the reasons is the temp folder security permissions being messed up, so it can’t write and open it, but that would not be the only reason.
As some sort of starting point, is it only Messenger MSIs, or all MSIs? If you need a random thing to test this, here’s an open source acoustic analyzer I was using the other day.
If that fails too with the same error, and existing possibilities aren’t working, then it’s a Windows problem and you’ll need someone to be on your machine to debug it for you. Alternatively, if you want something to try yourself, you might consider a repair install, which amounts to mounting/using a Windows 7 install ISO/disc, running the Windows setup from within Windows and telling it to “Upgrade”. The “upgrade” effectively replaces and fixes the system components while retaining your applications and files. You might have to setup your nice colour scheme afterwards though.