Remove unwanted desktop icons?

Hi all,

I realize this question has been asked numerous times, but nothing seems to answer/address my specific problem. When I opened my computer today, I have three new (I had nothing to do with creating them/putting them there) Microsoft Excel sheets on my desktop. When I try to drag them to the trash, it says that "File XXXXXXX cannot be moved to the trash because it can not be deleted." I tried shutting down Excel, nothing. When I try to locate the files through the Finder, they don't show up under desktop, or even when I search "This Mac"

Any thoughts on something else I could try? Thanks!