The onboard graphics your computer has doesn't support widescreen or resolutions higher than 1280x1024.
You need a PCI video card - something like this:
http://www.newegg.com/Product/Produc...82E16814130289
More:
http://www.newegg.com/Product/Produc...048+1069609642
Installation instructions:
http://h10025.www1.hp.com/ewfrf/wc/d...=92919&lang=tr