Install FSX after FSX-SE?

After a full reinstall of Win 7 I installed FSX Steam. All was well for several months but now I am constantly getting new problems with the sim. Things like "Error ID = 28 Unable to install message filter", Steam pops up/disappears, etc.

So, my question is should I uninstall all of Steam, FSX, etc and then install FSX ? Otherwise, how about installing FSX on a separate drive and leaving Steam?

I had high hopes for Steam but it doesn't help much when problems arise. About the only fix(temporary) is to revalidate files .....usually 2 or more need to be corrected