Buy a new motherboard and another video card. You can find lots of graphics card/motherboard combo deals at newegg.com

Find out what type of ram you have and make sure it will work with the new board. Also, make sure your CPU will work and that it will fit in your case. I stopped buying brand name systems years ago. The only thing I buy now are dell laptops. If you start getting into building your own system you will have more power over the quality of parts that make up your pc. It also gives you better options for future upgrades.