HDD ID Utility will show your HDD serial number. It is a programmer's tool.

FEATURES:
- use a very small DLL to show the IDs of the HDD partitions and load them in the registry
- you can directly import function from DLL or you can read the key that was stored in registry by the program for you
- it is really small (the DLL size is only 15K)
- it is freeware
- it doesn't need to be installed/uninstalled