Is that CS3? If you do not have the disks use this link. http://prodesigntools.com/how-to-get-prior-adobe-software-versions-cs4-cs5.html
Follow instructions exactly and then burn a disk of the installatiion files and put away for possible future use.
Are you referring to Photoshop Elements 10, or PS CS 3?
I will Move your post to that forum, where you will get better assistance, if you mean Photoshop Elements 10.