Check the board for white lettering.. it's called a silk-mask. It should give you the model number. Also, post the bios id string, that might help. Or you can use this software that usually will help:
To find make and model of pc hardware, EVEREST Home Edition is a free system diagnostics, system information program that will id most hardware onboard a mb. as well as the actual motherboard.
Alternate Everest download link: (offers 2 sites to dl program from)
Run the program and then:
Click on Computer
Click on Summary
Right hand window (hardware) if the text is BLUE
this is a link to the web site for that particular hardware.
If you have additional questions or need further help, please post a SUMMARY report from Everest.