You'd think going to the Adobe website would be the natural choice. However, the Adobe site has the install files broken up into several different .exe files and the word around the web is that it's not easy to install.
My path turned out to be much easier - I went to TechSpot (no, I have no association with them, and only discovered TechSpot for the first time for this project). I googled 'free CS2 for Windows 7'. It led me to this site...
http://www.techspot.com/downloads/3689-adobe-photoshop-cs2.html
Notice the serial numbers for Windows and for Mac versions of CS2 on this webpage and write them down. I then clicked on the blue "download now" icon and it offered whether to do for Windows or Mac. I chose Windows. It asked where to download the 340Meg installation file PhSp_CS2_English.exe and offered a default, which I took. It took a few minutes to download on my DSL connection. I then clicked on the Windows start icon at bottom left, and run, and giving it the file and location of PhSp_CS2_English.exe . After that, it was just a matter of following instructions. Within a few more minutes, I had CS2 installed and working on my 64-bit Win7 machine.