This newly appearing symbol has me stumped. It is a red circle with a white exclamation point inside. It sits on the lower right corner of the icons on my desktop. It has appeared on files as well as entire folders. I've searched through my computer's "help" section to no avail. What does it mean?

Would this be on your Amiga? Your VAX 11/780, or your PDP-11

By that I mean we need more specifics... not all computers have the same OS on them.

Usually this means that there is corruption in the headers that link the icons to the actual exe files for the apps or the folders where the data resides.

Might want to try these two steps

First do a serious online scan with this link

Then do a serious drive optimize here

Both free