When I open permon.msc and click on the performance monitor, then close
perfmon.msc, mmc crashes.

I've run sfc /scannow, and it can't replace perfmon.msc (although it does
recognize that it is corrupted). I read around a bit and tried manually
replacing it by copying the stored perfmon.msc from the winsxs directory, but
that didn't help.

I've tried creating a new perfmon.msc by opening mmc, adding the performance
and reliability snapin and saving it as perfmon.msc, but that didn't help.

The weird thing is that if I open the snapin in a new mmc, or in
compmgmt.msc I don't have this problem. It only occurs when I run the one
from the system32 folder (regardless of whether it's the original, or a new
one, that works outside of the system32 folder, replacing the original).

Any thoughts on this one?