What motherboard do I have?

In Vista, where do you go to check what motherboard you have? I need to upgrade and don’t know what is compatible with my computer. Unreal Tournament 2004 is running at much lower framerates (yes, I did reinstall ATI drivers). Perhaps RAM will help it. Also I need more space. Do you know if most computer have 2+ slots for harddrives?

My specs:
[]3.2 GHz Pentium 4
]128 MB ATI Radeon X300
[]1 GB RAM
]80 GB HD 7200 RPM