Deleting/renaming files my computer thinks is in use

Hello,

I am having problems deleting/renaming files. I get a message that the file is locked and in use by another program. I know that it is not in use by another program because I am the only one that can access these files. This started happening shortly after I got the computer less than four months ago.

So far, I have not had this problem with files other than Word or Excel. I am running the 2007 version of these Microsoft products.

Sometimes I can solve the problem by rebooting, certainly not a preferred method.

Your suggestions are most welcome.