error "the installation source for this product is not available. Verify that the source exists and that you can access it."
Resolution:
extract contents of rollup and run the install again.
to extract the contents of a rollup
open a command prompt
msiexec.exe /p" c:\location of folder with rolluppack\rolluppackname.msp" /a"c:\location of folder with MPS\MetaFrame Presentation Server\MPS.msi"