It's available in the MP. It corrects bad references. BUM file calls if you use Poser 5, say, or bad file names, missing textures, that kind of thing.

You'd be amazed at how many products have bad references. Even DAZ, RNDA, and PoserPros, which have pretty good QA, have released products with bad references. For example, a texture call to E:PoserMyProducts.... (Looking on the merchant's own computer for the texture, instead of on the buyer's.) Textures named red.jpg or brown.jpg - so common that a texture from a different product that uses the same name is likely to be used instead. Or textures that are misnamed or missing altogether.

These bad references slow down Poser, even cause it to crash. Running CR Pro can speed up Poser a lot. It's worth it, if only to delete all the calls to BUM files in old P4 products. (Assuming you're not using P4, that is.)

There's also a free version of Correct Reference, that does a lot of what the Pro version does.