I just replaced the motherboard in my PC and as such had to reinstall Windows. When I backed up my program files, it didn't get Steam's files for some reason and now I'm reinstalling everything. I've lost every one of the custom songs that I've downloaded, so I need to know if there's a quick way I can look at things that I've viewed.Any help or suggestions here?

Um, I'm certainly not the expert on that subject, but, I don't think you have a way to do that.

If you only viewed & downloaded the song, then I think your out of luck. If you left a comment thanking the charter, then in the submitted CDLC (BETA) section any song you left comments on will have a star instead of a dot in front of the listing. 

You could try using your browser history

Did you follow the songs you downloaded? If so, you can use the "Favorites" view in Search.

One more solution. Check your download folder (maybe you had a default one, or one you have specified) and there you should have the files before moving them into dlc folder in Rocksmith....If you didn't, I highly recommend that you do now such a folder. I always keep a copy of the files as you can have total control on them and you are always able to make changes in the game without losing everything.

 

Cheers and good luck