Re: new motherboard make computer better?
A new motherboard won't make the computer faster, so a new one is pointless to make it faster unless you are going to upgrade other components - eg cpu, memory etc.
I would get a new motherboard, cpu, and memory, and possibly a PCI express graphics card (if you don't have one already or if you have an AGP card).
You can keep your hard drive with your stuff on, your sound card, and probably your power supply. This will make your computer faster, but a new motherboard on its own will not.