I moved this thread over to the Police Quest series page so you might be able to get some help.
The technical experts of Sierra games are at The Sierra Help Pages. Be sure to check the forums there for a definitive answer but I’d be willing to bet you are looking at an XP to Windows 7 issue – of which there are many. I am personally running a XP virtual machine through Windows 7 but in many cases I have to use an actual XP install (either on the same machine or another) to get some of the XP games to play (Kings Quest: Mask of Eternity is especially resistant to running on Windows 7 and SWAT 3 was a close contemporary to KQ8).
Either way, good luck. I wish there was a better answer but it seems the passing of time and operating systems wreaks havoc on those of us who want to hang onto and play our older games.