Changing where image files are located?

When I first began adding items with image files, the image files were automatically ending up in "archive/files". At some point, the image file links on the item pages began to point to non-existent file folders of the pattern "files/download/40/fullsize" (40 being the item ID number in this example, and the "files" folder not existing). When I click on the link to the image now, I get a "not found on server" message, and of course the images are not appearing on my site. Is there a way to manually make the items point to a given folder to find the image file (e.g. back to my "archive/files" folder)? I'm not using ImageMagick.
Thank you for your help!

This problem was solved by getting ImageMagick to install properly.