You actually unknowingly answered your own question to the problem at hand with your system crashing periodically.... 15 games installed. Windows never has, never will claim that it is game friendly. Games run and produce conflicts, bugs if you like, within Windows. The only way you can avoid system failures is to limit the games you load to one at a time. You have the game your playing installed, you play it, when you finish it you remove it completely from the system. You then install the next game.

Having multiple games loaded which are already buggy at the best of times as Windows does not guarantee to be compatible with them, let alone play nice with other game files installed on the system. You must understand that games use some of the same files in Windows OS to run. When you have more than one installed, you now created a conflict of interest in those files, hence you crash Windows.

If you use the safe method which is recommended by most computer experts, you install one game and uninstall completely, restart then install your next game. I have run mine that way for a long time now and never crashed Windows. When I used to run several games on the system, just having several installed that is, Windows used to crash due to conflicts.

Best thing... you sound quite computer literate, which is great.