All hope is not lost, you have a few options.
1: Get a graphics card that supports 3 or more monitors. Most ATI cards do and a few specialized NVidia cards will as well.
2: Try to take advantage of the integrated graphics on your motherboard. This may not be an option if you don't have integrated graphics but it's an easy free option if you do.
3: Use a tool like a the Mattrox Dual Head which makes the computer think it's plugged into an ultra high resolution monitor then splits the image to two different monitors.
4: If your computer has USB 3.0 you can buy an adapter that goes from USB 3.0 to a monitor.
5: Install a second PCI graphics card, not a PCI-Express but a standard PCI. I bet you have an open slot, the performance would be terrible but if your not planning on doing media on the third monitor it would probably be okay.
6: Buy a new computer that supports 3 monitors.
I would be happy to elaborate more on any of these options if you need me to.