Driver not visible under Device Manager

Hi ,
I have a volume level filter driver which is being shown in Device
Manager, under “Non Plug and play drivers”. Strangely even a simple
helloworld.sys with a unload routing gets listed under the list with no
extra effor, and so does other volume level filters like volsnap. Iam i
missing something or iam not doing some registration.

Thanks & Regards
Girish