What could slow down couple of my MS Excel files?

[aromes]

I have a file of 8MB (containing just calculations..no macros) that takes 1 minute

to save even a minor addition such as adding just a number in a cell! And scrolling in that file is extremely slow. I have same problem with light-weight that I create locally or on my network shares. It's hard to troubleshoot since some other excel files I would create or work with are fast to be saved (on same computer, on same network drives). So why some files would be slow and others wont (no matter where they are located)!

I have MS Office 2002.

Windows 2002.