I have changed the cmos battery then I turn on my computer but there's no monitor display, and I try to check all wires and change the video card and monitor also but there's still no screen display so how can solve this problem?
Note: I only changed cmos battery and do nothing else.
In the absence of one iota of information about your system, I will assume you have a discrete GPU, but your mobo also has integrated graphics. Whichever one your monitor is plugged into now, switch to the other one. You should get a display, and can then go into your BIOS and choose the one you want.
But before i change the cmos battery i can start computer with monitor display and 'beep' sound. then I change cmos battery i start computer with no monitor and no 'beep' sound. so what is the problem?
removing the battery probably cleared the cmos memory but just in case, have you tried to clear it manually too? (the manual of your motherboard should have instructions on this). See if that helps. Also, try and remove all equipment that is not essential to start the boot process (e.g. hard disks, peripherals) and leave only cpu, video card and memory. You can also remove the memory and see if the motherboard complains by beeping several times. Was there a particular reason you removed the battery in the first place?