Problem Converting to 2007

[sg]

I have an Access db that is in the 2000 file format. Every time I go through
the steps to convert it, Save As, Access 2007, I get the message that I
attempted to open a database that is already opened exclusively by...

I have to open it to convert it don't I? I double-checked and the database
is set to open in shared mode. I have tried the same procedure with a
different database and also on a different computer - always get the same
message.

How do I get it into 2007 format?

Thanks in advance for your help!