you should be backing up anyway.
if i were to upgrade an OS drive i would do a fresh install rather than transfer the original install. in that case i would save all important data and everything i wanted to keep into a certain folder (say C:\backup), take it out put the new one in and install the OS. then i would just put the old drive in an external case, connect it by USB and copy the data accross
alternativly you could use something like acronis to transfer the partition to the new drive