Read-only simply means you can't write to the file. You should still be able to view the contents.
First thing. Is this a floppy disk? or a CD-Rom Disc? If it's the former then there is a black slider on the back in the upper left corner. The up position is read-only, and the down position is read-write.
If that isn't the problem, but you're able to open the file at least to view it, then you can do a save-as and save it as a different file name and manipulate the new file.
The only other technique I have in my arsnel is to use
OpenOffice to open the file. It's capable fo reading .xls files just like Excel, and best of all it's free.