I want to buy a new Graphics card?

What slots do you have available and whats your price range? Also, how good is your power supply? Without all this information its impossible to recommend a 'good' graphics card. If you just want dual monitor and you don't care about performance, AND you have a PCI-Ex16 slot, go for the cheapest new-gen card you can. (Like a Geforce 8400, or a Radeon HD 3450).