CS2 cannot save as or read PNG

I recently purchased and installed Photoshop CS2, but when I went to open a PNG file, I was informed that CS2 could not read the said file. I then proceeded to open several other PNG files only to have the same result. I tried to save a PSD as a PNG only to find that PNG as well as most of the normal array of extensions were missing from the extension selection. What is the problem and how do I fix it?

Where did you buy Photoshop? I can read and save .png

Do you have a PNG.plugin in your Photoshop CS2 > plugins > Photoshop only > file format folder?

You've moved the application, or deleted some plugins.