Just a FYI, if you have a full license of Photoshop 3.0 from 1994, and an upgrade license of Photoshop 5.5 from 1999, the 3.0 will not even begin to install on Windows 7.
Skip straight to installing 5.5, and when it asks to validate, choose to let it check the original media for 3.0, then keep in mind that the serial number it will request in the next step is the one for 3.0
Everything just worked after that, and 5.5 ran fine under Windows 7.
Note that this is NOT Photoshop CS5, it's an ancient version.
