In Tools – Options – Environment – Documents, there’s the option Allow editing of read-only files; warn when attempt to save.

If this option is checked (my personal preference), you’ll get prompted whether you want to overwrite or save the document as something else.  My thoughts are if i’m editing the file, i want to overwrite it eventually.

Overwrite Read-only File or Save as message box

If this option isn’t checked, you’ll get prompted whether to make the file writeable or do an in-memory edit.

Edit In-Memory or Make Writeable prompt

Technorati tags: VS2005Tip, VS2008Tip