We've recently had many people uploading their old mod collections and from experience I can say that we already have 90% of the material people upload. We outright reject files that are bitwise identical with an already existing file on the archive, but of course there are often some variations (e.g. because people re-saved the file in another program, or because the file has been uploaded to a BBS which added their own advertisements in the sample text). Searching by song name is often a good way to find such duplicates. Simply put: If you don't do that, we will have to do that so you're just pushing the work to someone else if you don't. If the files are by a well-known author, you can be rather sure that we have them already.
TL;DR: Yes, you can upload the files once you've got an account on the archive, and you have to select that they are not your own files upon upload, but please check song/file names if the file is already there.
