If you try to install Proseries into any directory except c:\ProWinYY (where YY=year) then your install will fail with "There was a problem installing Entitlement Client", Error 1619 or 1601.  No one in tech support will be able to help you; they will claim there is some problem with your hardware or operating system.  I believe the problem occurs because the Entitlement Client has this particular directory hard-coded, so when it tries to read from itself in this directory, it can't find itself.  This has been an installation bug for several years and has cost me a lot of time to figure out on my own.