I just installed a new motherboard onto my case, got the cpu in, and all the connectors connected (I think?), but the computer won't turn on. hard drive, ram etc, are all installed, I really don't know what to do. please help me. thanks. later then.
You could have gotten a dead on arrival motherboard. Be sure to find out exactly what is wrong, and if it is the motherboard, send it back before your warranty runs out (often just 30 days).
I'm assuming the CPU, PSU and RAM were already tested as good in another system? If not, they are suspect too.
We really need more information for a better diagnosis. What precisely does it do when you turn on the power switch? Also, does removing the CPU or the RAM change the symptoms? Do you have a multimeter to test the power supply with? Is the power button connected to the right pins on the motherboard?
This may sound like a dumb question but are you saying that nothing powers up or do you mean the computer won't boot up to the operating system? If it is the latter it is because you can't use the hard drive with the new motherboard. You have to format the drive and install new. But if there is no power going to any of the components then you have to verify that the pcu is working, then take it from there and retrace everything you did. Sometimes it might be the littlest of things. Try going over it again before you start going crazy.
But like the previous poster said it would be more helpful if you gave us further more in depth details.
Would like to help. However more info is needed.