I have an A7N8X-VM Asus motherboard, can I change it with an Asus A7N8X-X board, or what is the difference between them, what is the difference between the VM and the X board
The 'X' is what's commonly called a 'full ATX board' the other, VM, is a 'micro' board, meaning it's a smaller cut down version to fit smaller cases, has less PCI slots ... apart from that, there is no real 'difference' in the two specs.
No point in changing the board for the same board ... save your pennies for a better system.