Your onboard graphics (integrated Intel Extreme Graphics) will not support all of Windows 7 features even if you did have drivers to installed.
You can purchase a PCIe x16 low-profile graphics card. Please make sure it is a low-profile card. If I am correct, the computer will not support a full height graphics card.
I'm currently using a Radeon HD 4350 low-profile card. A similar card will do just fine for you.
Checkout these cards at
Newegg. They are all low-profile, however you may not can use the ASUS cards. For some reason they put a huge cooler on them, making the card twice as wide. The ASUS cards may not fit in the alloted space.