Whenever my friend opens a certain spreadsheet in Excel, it creates another copy of the spreadsheet in the folder it's saved in. So he still has his ORIGINAL but Excel KEEPS adding all these "dummy" files in the folder along with his original. What causes this and is there a way to fix it? Thanks!

JonathanI believe these are temp files Excel creates incase your original file gets corrupted while you are working on it.  If you don't want to see these files try going into Windows Explorer or My computer and finding the location of the file.  Then click Tools, Folder Options, click the View tab and click the Do not show hidden files and folders radio button.  This should make these files disappear.Thanks a lot! I'll give that a try. I've gotta talk with him first to see if he wants to actually delete them or just hide them. Is there a way to keep excel from making those files at all? I don't think it's a good idea to turn this option off incase of a power outage or corrupt file.  This enables you to recover your file without losing any or much of it.  If your friend doesn't mind not having a temporary backup I believe I found a way to turn this off.  In Excel 2003, click Tools, Options, and select the Save tab.  Under workbook options, check disable autorecovery.  I believe this should stop the temp files from being CREATED.  Again, I don't think this is a good idea.
Hope this helps.   
Thanks for the help! I'll talk with him and see what he wants to do about it. For now I've just hidden all the files that were in there. I guess he could go in and manually hide them all but we'll see what he wants to do. Again, thanks for your help!     Your welcome.