"opened exclusively by another user"
 

We are running a very basic office network, and often have to share files
hosted on my computer (not a "server"). We have no problems opening files
such as MS Word, CorelDraw and others, but Excel spreadsheets (always) and
Access databases (sometimes) will not open and we get the message about being
opened exclusively by another user. The problem is that the files are not in
fact open, and I have shut down Excel on my machine. We have tried rebooting,
but I really have no technical knowledge beyond that point. We have enabled
file and printer sharing, and allowed remote users to edit my files. The
files in question are not read only. Any help would be appreciated. Thanks
in advance.