Migration from Mac to PC

I am attempting to migrate my Lightroom setup from Mac to PC.  I have transferred my photos and both my catalogs (not sure why I have two) to the PC and now have two folders: Lightroom, with a week's work of the new stuff imported directly to the PC, and OldLightroom, with all the Mac stuff.  In the end, I'd like to merge it all together, of course.  A more immediate issue, though, is that the pathways to the pictures have changed and I don't know how to reset them such that my old catalog can see the old photos.