Windows 7: Problem with one of the system sounds win7

At least one or possibly more of my system sounds are not triggering. I get the startup sound and the "clicks" from opening folders and the empty recycle bin sound, but not critical stop (I think that is the one) for when you try to overwrite a file with the same name, etc. There may be others that aren't working, but that is all I know of. I actually copy many files all the time and that sound was nice to have.

All the files are there in the windows/media folder and play fine in my audio player. All the sounds play fine with the sound scheme "test" button. I'm using windows default scheme. I have no custom sounds or anything.

Everything was working fine up until a few days ago. I install/uninstall things all the time so I don't know what if anything caused this. I think it is only that one sound that is not triggering anymore.

I also ran virus/malware scans and found no problems. I also ran the system file checker utility, Sfc.exe, with no results.

Does anyone know what is going on?