Need to uninstall CS3 Extended - LOCKED, dead product

I inadvertently installed a copy of CS3 extended, thinking it was a new version of CS3 and not realizing that an older version of Photoshop was required. After I realized my mistake, I found a used version of CS3 and installed it. Unfortunalely, the 30 day trial of the Extended version is over and I cannot access my standard CS3 version; it keeps defaulting to the upgrade panel. I've tried uninstalling and reinstalling just the CS3 severl times to no avail. Please help