Serxho :
Yeah files ,music,movies,etc, but how????
The easiest way is with a little prep beforehand.
Create a few folders, completely outside your User account. MyDocs, MyMusic, etc.
Copy all the stuff you want into that new folder structure.
When the OS is installed on the new drive, connect the old HDD, and simply copy those things over.
Why do it that way? In your current install, the User folders (Documents, Music, etc) are tied to your user account. Accessing them after the new OS will be just a touch more difficult. You can go in and change permissions after the fact, but that little bit of prep beforehand gets rid of even that step.