Dual Monitor only mirrors

Im trying to set up dual monitors using Ubuntu 9.10. I am using a radeon HD 5450 ATI graphics card.

When I try and go to the display settings its coming up as an "unknown" monitor. and the second monitor isnt showing up at all. I dont know what else i can do to fix the issue since im new to the linux world. If anyone can help me fix this I would be greatful.....thanx in advance