I encountered a problem with Adobe Photoshop CS2 version 9.0 on a system where Photoshop would not correctly save a file when the "Save As" option was used. You could pick whatever format you chose, but Photoshop would always save the file as a Photoshop PSD file. Oh, you could have it put on the extension for the desired format, e.g. somefile.jpg, but the contents of the file would be in PSD format. If you chose "Save for Web" instead of "Save As" you could save the file correctly in the chosen format, e.g. JPG.
I was finally able to resolve the problem by holding down the Ctrl, Alt, and Shift keys while starting Photoshop to have it wipe out its stored settings
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