Boot issues with Ubuntu 12.04 on VAIO netbook

We are giving away our slightly used VAIO netbook to someone, and we are having issues booting it up after doing a clean install of 12.04 on the system. Our system initially had version 11 of Ubuntu on it, and the person we are giving the netbook to would like to keep a Linux system on it. So we decided to do a clean install of 12.04 from a bootable USB drive , overwriting the partition in order to erase personal data from the previous setup. Unfortunately, it now seems that the new 12.04 OS will only run when the USB drive is attached at startup. If we try to boot the netbook up from the hard drive it hangs on a black screen after the computer boots (after post I believe)
We are not sure why this is the case and would appreciate any help in this matter.
Thanks.