I have a problem running 3cx on some of my windows 7 workstations and not on others. The one that is bugging me the most is an i3 3.07 GHz with 4.00 GB of memory. This is a 64 bit machine. Right now I have 12.5 installed, it won't run. The system manager says the program starts but then it just quits. History: - Clean install of 12.5 for test. It worked. - Upgrade to 15 and the system hung up at the C++ 2015 Redistribute at the end when it is trying the install the .msu - from there tried to remedy the .msu problem - gave up and did a system restore to previous version and tried re-installing 12.5, now that won't run. Why does the program start (12.5 or 15) and never complete? There is plenty of memory and the software runs on lesser systems. Thanks for your help.