Finder and folders

I've just had a new disc installed on my IMac. Since then I find that when I create a new folder on my Desktop using Finder, the new folder contains all the existing items on the Desktop. If I delete any of these items I delete them not only from the new folder but from the Desktop as well.

I thought it may be a problem between my iMac and ICloud but having unclicked the Desktop option on the iCloud it still occurs. I can find no help anywhere for this problem but it essentially makes my Desktop unusable as a temporary storage option.

I'd be grateful for any help.

Thanks