To find out extensive system information you can download and run Belarc Advisor:
http://www.belarc.com/free_download.html
If you got the whole system complete it's very likely that the graphics card is Asus too.
On the Asus link, there's a link (Asus navigation wizard) to direct you to the driver download page, or you can navigate yourself by the General Download window on the right - (top to bottom) choose Graphic Card then NVidia Series then EN8800 Series and you should be directed to the Asus Specific driver page.
(Bottom left is a set of links with Specifications/FAQs and a discussion forum you might want to look at.)
Expand VGA and, after a short wait, a window should open with driver downloads for various Operating Systems; you want the second one. It's a zip file so download it and extract it to a directory. See if there's a setup file in there.
If not you'll have to install the driver manually via right-click screen -> properties -> settings -> advanced -> adapter -> properties -> driver -> update -> don't connect -> manually choose driver to install -> navigate to the folder -> click ok.
Hope it's gonna help.