actually previously i had 80GB DD and i purchase another had160 GB and in both HUD have same os but i installed everything in previous hdd thats why i want to show my installed hdd then after show 160 gb hdd
You have your 80gb hard drive with the OS on it and you want to add another 80gb hard drive and make it a raid setup and be 160 gb , is that what you want to do? To do that you need both drives formatted and then in the raid bios set tham up in raid 0 and that makes them 160 gb to be used to install the OS on to. If you have the motherboards owners manual it will show you how to set the raid up and what button to press during boot up to get to the raid menu.
You're a little unclear. It sounds like you have an existing 80 GB HDD with your OS and you want to add another 80 GB HDD to make it 160 GB. I'm not sure what OS you have but Win XP/7 permit the spanning of drives to form one disk. I don't recommend it for the simple fact that if one drive fails you loose the whole thing.