Can't launch the Modelsim-Altera Software

Hi! I also had this problem, and in my case the solution of adding the '\' was not enough. I had one more configuration issue, and thought I'll post my problem/solution here for you.

I am running Quartus II 16.0 and ModelSIM Altera Starter 10.4d and had all paths set right. What helped was to also set the correct EDA tool in the project settings. To verify, go to Assignments > Settings > EDA Tool Settings and make sure you have ModelSIM-Altera selected under Tool Name. Similarly, go to Assignments > Settings > EDA Tool Settings > Simulation and do the same. Initially I had it set to ModelSIM, and Quartus was right to not find the right executables.