At first it may seems it is very easy question and some body may be trying to give me advice to try Google, it may be so. But for me it is very hard I have try Google, Stack
see this
http://www.codeproject.com/KB/system/GetHardwareInformation.aspx
just download demo from there and select "data storage" tab and select Win32_DiskDrive from this you will get information all the Disk drives(HardDisk) mention below and see one property "SerialNumber" after sectorpertrack and before signature property...
