Hi,
Firstly, WELCOME TO TECHIMO...
What you seem to have done is disabled the GPU in the "Setup" or BIOS. What you will need to do is to get back into this area and re-enable it.
To get into the BIOS you will need to press <delete> when you first power the computer up. Once you're in the BIOS you will need to find where the setting you changed is.
I'm not the best person to advise you on where this is, but I would guess it is likely to say something along the lines of "Enable Graphics Card", "Enable PCI card", "Enable AGP card", or perhaps even "Graphics Card" then a sub-menu that would give the options to enable it.
Let us know how it goes...