Is it possible for ALL of my mods & CC to be corrupted

zoe3007​ If you had moved all those mod files onto an external drive that wasn't in the right format for the files, yes, that could easily corrupt all your files. There are likely other ways that could happen too. If every single mod copied back in blocks launch, but a fresh download doesn't, then yes, you likely have no option but to redownload. Think of it as an option to start fresh with just what you really use, well organized for the future.