Can you add ACT! install to the global software deployment list? Download link is here:
@Nick_Penhale have you been able to find any details from the vendor that would suggest their installer supports silent installs from the SYSTEM context? My googlefoo may be failing tonight but a quick search I was not able to find anything.
I found a help article in their KB but it does not seem pretty or as easy as other programs, it might not be possible considering: Act Help Center
Just from a quick look, the best approach might be to use ProcMon to check the command line parameters used when it is installed in GUI mode. Then use Extract-WithTool to unzip the main executable and work with the resources inside it. I’ve had to do this with a few, and while it is intensive, it feels pretty rewarding once you’ve got it