A while ago I did an unsuccessful posting about how to avoid the 'read-only' problem with Office 2003. Ton Stegeman however, did not leave it that way and created a great feature that gets rid of the very un-user friendly behavior of Office 2003 and SharePoint:
´Users then make changes to the document, hit the save button and get the Save As dialog. If 'Require checkout' is enabled, they need to save the document using a new name, because the document cannot be overwritten. It is pretty hard to explain and for users it is hard to get used to it.
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I have called the document library an "Edit Document Library". You can download it from our CodePlex site. Before you install it, please note that you will only benefit from this when you use Office 2003. Office 2007 behaves like you would expect. After running the installer, and deploying the solution to your web application(s), your top level sites have a new site collection feature called "Edit Document Library":´
Kudo's to Ton!