Help Installing/Un-Installing Photoshop CS3

Hi
ive downloaded photoshop cs3 again though id give it a go was bored

ive come to installing the software onto my laptop and it says theres already a photoshop cs3 installed ive searched for program files and found nothing/

so i come to uninstalling hte old software and it says that the uninstallation cannot be completed till internet explorer is closed i dont have the program open at all

was wondering if anyone could suggest a way to get shot of the old software so i can install the new one

ive restarted my computer to see if that would work that hasnt helped either

thanks in advance