Games - for Steam games, you can install te client on your HDD. Then you can tell the client, in Settings, where exactly you want the games to install
Music, Pics, etc:
Create a few folders on the HDD MyDocs, and subfolders of MyDocuments, MyMusic, MyPics, etc
Move anything in your current Library locations to those new places
In Libraries, right click on Documents, select Properties
Add the location you created above
Click on "Set Save Location"
Now, those new locations on the HDD will be the default.