Navigate to:
HKEY_LOCAL_MACHINESOFTWAREMicrosoftWi
I.e. C for your C: drive.
To change the icon for that drive, create a key inside that one called DefaultIcon and set the path of (Default) to the location of your icon
eg CDefaultIcon
then (Default) = D:DocumentsC Drive Icon.ico
To change the name of that drive, create a key in the drive letter one (eg C) called DefaultLabel and set the (Default) to what you want the drive to be called.