If you reformatted and used an install method outside the recovery disc set. You will have to manually install the drivers. Some of the devices may be loaded with Windows, some simply will not be part of it. Heck, some may be located with a Windows Update.
You could go to the support page for the device and download the drivers there. Or go to the manufacturer's site (i.e. nVidia) and download the driver that suites your operating system and card series.
I would suggest sticking with the Asus support site, since it looks like you do not have a whole lot of saavy with computers and such. You will see all the drivers and most if not all the software that shipped with the machine.
Just select the exact machine you have, then after you click the link to it. The Operating system you are using. Making sure to select 32bit or 64bit versions. Depending which one you are using.
http://support.asus.com/download/ModelList.aspx?SLanguage=en&keyword=G51J&type=1You should be good to go and find all the drivers and software you need.