I need to change an specific high resolution image that is a .psd but in mac format (.hqx) to a win .psd

PSD stands for photoshop, you can get photoshop to work with mac. Try here http://www.adobe.com/support/downloa...form=Macintosh

If you're running Photoshop in Windows with all of the file converter options enabled during the installation, then I would have expected that the Open File dialog would allow you to select HQX file types in the File Type list at the bottom of the dialog. I've never used Photoshop, by the way, but that's how any decent program like that ought to work.