You will have to redownload all the games. Also You should just transfer files. Taking the whole HDD over to your new PC will mess up the OS boot and just be a pain when finding files especially if you plan on backing up the hard drive it will just create multiples of the files. It would be easier to just get the files you want,put them on a USB stick or backup drive, then transfer them. But if you want to use that drive still get all the files you want off of it then format it.