To delete stuff is right click and select 'Delete'. Is this in your Start menu, or your start-up folder? Or somewhere else?

I don't click anything to ask for it. I think I've tried right click.

Plenty has been written about how to stop this, so I won't retype it. Here's a couple of links. Dp a search for drop box popup on startup you'll find a heap of help to disable it.

https://www.howtogeek.com/686527/how-to-stop-dropbox-from-opening-at-startup-on-windows-or-mac/

https://geekrewind.com/how-to-stop-dropbox-from-opening-automatically-on-windows-11/

https://www.ghacks.net/2014/11/10/how-to-stop-dropbox-permanently-from-autostarting-on-windows/

The first/regular option was to "Open" Dropbox, which involves being signed into an account to begin with. I have not signed up for an account.

So the Alternate method, by Task Manager (Cntrl + Alt + Del), was simple and fast:

"An Alternative Method for Windows PCs
On Windows, it is also possible to prevent Dropbox from opening at startup using Task Manager. To open Task Manager, right-click on the taskbar and select "Task Manager." In Task Manager, click the "Startup" tab. Select "Dropbox" from the list of applications, then click the "Disable" button."

Personally, I hate stuff running on my computer without my permission. Eats up processor cycles.