P4M266 and VT 8751 are both chipsets, not motherboards. These chips could be used on any manufacturers motherboard.
You will need to provide a more accurate mb. description before we can help. ie: bios id string, motherboard brand and model, etc. If you are unable to identify the motherboard properly, use this program:
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.