title explains all
I have a 120gb with os and games and i want all that into my new 500gb without reinstalling anything
This is what I do, I use Acronis and clone the 120G to the 500G you can do it with the free 30 day trial version of Acronis.
First Install Acronis on the 120G source HDD, to complete the installation Acronis will have to reboot the computer, after the reboot and Acronis is fully installed, shut down the computer and connect the new HDD.
Boot up the computer and open the Acronis program and go to Manage Hard Disks, select Clone Disk, use the automatic cloning feature, and give permission for Acronis to take full control and reboot, the cloning process begins, the computer will reboot.
After completing the first phase of the cloning process Acronis will shut down the computer, at that point you disconnect the 120G source HDD from the computer, and with only the new 500G HDD installed you restart the computer, and Acronis will complete the cloning process of the 500G HDD with drive letter assignment, and you'll be fully operational with your new 500G HDD.