Please try the below mentioned steps:
Also like to mention here, ADE 4.0.x is compatible with Win7, for more details Tech Specs | Adobe Digital Editions
This did not work. Now what?
Since you are using Windows XP your computer is fairly old. With our old XP computer with an AMD 2800 processor I had to use ADE 1.72, even ADE 2.0 would not install and I got the same error message. I believe 1.72 is still available at:
First uninstall ADE 4 before trying to install 1.72.