Open up the document in CS2 that you want to resize.
The go to "Image" on the menu bar, and select "Image Size...". (The shortcut alt-ctrl-I may also work)
Then type in your new size in pixels, and press ok and the image should scale down 
If you uncheck "Constrain Proportions" in the image size box that pops up you will be able to enter both pixel values separately as opposed to them changing automatically on what you type.