Software Deployment

Hello,

I am running into some real problems with multiple versions of ISScript and am unsure how to proceed. I have a setup.exe for Pictometry's "Electronic Field Study 2.7". The setup attempts to install the accompanying MSI (which will not launch directly - unsure how to bypass, there's no launch conditions, so maybe there's a ISSETUPDRIVEN property I can define or something?), but setup also uses ISScrip9.MSI and uses the Installshield Driver - but it's unable to do so - even on manual launch of setup.exe. I have preexisting installs of other ISScript engines and drivers (6, 7, 10, 11 & 11.5) because apparently Installshield won't be happy until they fill up my whole drive with their junk. Anyway, ISScript9's driver won't run while 7 is there I think - unsure. Does anyone have good advice on how to correctly diagnose and repair multiple Installshield Engine problems? I find Installshield's literature a little too deliberately oblivious of there being any problem or conflict between their various versions.
Also, a good link for a write up on how to remove an MSI's dependency on being run by a SETUP.exe and having whichever version of ISScript be available to it without installing the ISScript engine permanently? (We have a domain with only GPO for deployment, thus command line installations and uninstallations are not my preferred deployment model - I try to get all packages to be just an MSI or an MSI&MST at most). ISScript requirements have always vexed me, and many different ISScript versions exist on many of my desktops, more than anything I'd like to get a grip on the ins and outs of using/maintaing/troubleshooting & removing multiple ISScript versions.