If you can't run a game in Vista, there's usually an easy to find solution, which tend to be on the net.
I found Final Fantasy VIII crashed on start-up and Dark Messiah was extremely glitchy, all I need to do was download the nVidia patch for FF8, relocate the game executable to a different folder and get the latest update for Dark Messiah and both run perfectly under Vista now.
A simple google search provided answers for both...though I haven't found a solution to Summoner, mind you I couldn't even get that to run properly under XP either.
"Experience never provides its judgments with true or strict universality; but only (through induction) with assumed and comparative universality." - Immanuel Kant