I have all versions of Poser from P5 to Pro2014 running on Win7 64 bit without a problem.  P8 does have a library issue with IE 11 but since IE is not my primary browser, I unchecked the auto update box in the IE 10 about box.  I don't know what SMS so called experts are telling you but other than the IE problem (which SMS refuses to provide a patch for) Win updates are not the problem. 

What issues are you seeing with P7?  You will not have the same issues with P8 as P8 is the version that introduced the Flash library. 

Have you tried running them in compatibility mode?  If all else fails, you can create an XP virtual box on your system but I really don't see why you would need to.  Are all your SR's and video drivers up to date? 

Without know exactly what type of errors you are receiving for each version, it's difficult to give answers.