Go to This PC -> Users -> Username and right click on the folder (i.e. music) and select Properties. Then select the Location tab. Then select the location. What I do is I just change the drive letter to the HDD and leave the rest. Mine is D: so it is D:\Users\Username\Music etc.
As for programs default follow this:
The 64bit version has two versions of regedit. Make this change as well:
1.) Enter into Start>Run: %systemroot%\syswow64\regedit
2.) Go to: HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion
3.) Change the Path in DWORDs ProgramFilesDir, ProgramFilesDir (x86) to the new path, probably just changing the drive letter.
And there you go. Just be careful with the registry as messing something up can mess up the OS.