I came across this the other day. It was during a course I was teaching, so the timing couldn't have been worse. I don't have a screenshot, because I just wanted to get it sorted and didn't think "Ooh, I'll grab that to make my blog post better".
But essentially, in the "Add Counters" dialog box of Performance Monitor / System Monitor, all the drop-down lists were full of numbers, no names.
There's a way to unload the counter details for groups of counters and load them back in again, using "unlodctr.exe <group>" and "lodctr.exe <counter description file>" (or something like that). But this doesn't work in this particular situation, where all the counter names are lost.
The answer is: "lodctr.exe /r". The /r tells it to rebuild the sections of the registry that store this information, based on the list of what should be there (in the registry) and the backup set of .ini files. It takes a minute or so, and it doesn't give you lots of useful information – but if you're having this problem, try this and you'll hopefully see the success that I had!