Summarize the following:
Adobe Photoshop 6 and 7 use 16-bit installation programs. These programs have no issues running in 32-bit installations of Windows 7, but they cannot run in 64-bit installations of Windows 7. If you have a 64-bit installation of Windows, you will have to use workarounds to be able to install Photoshop. Take a look at our guide to determine which version of Windows 7 you are running.

Summary:
Understand why it won't install. Find your version of Windows.