It’s simple: create a folder called “Archive” on your desktop and put everything in it that you won’t need any time soon (today, say), but that you can’t bring yourself to delete, because you might need it after all, in a week, say.
The usual advice from productivity people is to sort files methodically into the right folders: “Work”, “Invoices”, “Catalogs” and so on.
With important files and documents, that’s what I do.
But what’s the point of cataloging files you probably won’t ever need? Besides, it’s a drag. Cataloging. For an ordinary person…
Just drop that kind of file into the archive. When you need it, look there; once a week or a month, delete what you never needed and catalog what you did. As a result, my desktop has lately looked like this:
(Image lost: a screenshot of my desktop.)