I have a msi g41m-p26 board and it turns on but doesn't display also the lan orange light lits up as soon as I connect power and it doesn't go off
The orange light is okay. It is just telling you that the other end of the cable is connected to a device that is powered up. The light will turn green once the LAN driver are loaded.
The display not working can be any number of problems. Make sure that the cable is plugged into the right port...some systems have more than one and since only one can be active at a time if the video is plugged into the inactive one you get a blank screen. Second, make sure the screen is working. Usually if you turn it off and then back on it will display the logo of the manufacturer or something about "no signal." Most displays also have a light telling you they are on or off. Make sure it's lit up.
Now, if the display works and displays the logo when you turn it on or at least a message saying "no signal" AND if you have the cable from the video to the system connected to the right place, but you still get no video, then the problem is in the system.
To test this we usually open the system and remove everything that can be removed because it is absolutely not needed to get the system started. We disconnect the hard drive and optical drives. We disconnect any devices, including keyboard and mouse, And we remove as many expansion cards (the ones in the pci or pciExpress slots) until we get the system stripped down to it's core.
The core of the system includes the power supply, the mainboard, the cpu, one ram module and the video components....onboard if it has onboard video (which I believe it does if my memory serves me), but a video card if it does not.
Once we are at the core we test. If it works we begin to add one thing at at time, testing as we go, until we find the bad part. If it does not come on we re-seat everything and switch to a second RAM module.
Once we have re-seated the CPU and RAM, if the thing still does not work we remove the CMOS battery for five minutes, put it back and try again.
If at that point, having tested about everything you can test, if it still doesn't come up, if we have a spare CPU we change that. If that too fails to fix the problem we consider the mainboard DOA.
Hope this helps.