I bought long time ago lightroom 3 on cd, and later online the upgrade : lightroom 4 , today i bought a new computer, i succeed to install lightroom 3 again , but how can i install the 4 ? Until now I only used it on one computer so I would like to use it on two computer( the old one and the new one )
You install it on the new computer the same way you installed it on the old computer.
The downloads can be found here: Product updates
Scroll down to where it lists Lightroom amongst all of the Adobe products
You will need your serial number to both LR3 and LR4