You probably need to run chkdsk /F like it advises you - however you need to boot the recovery console to do this. You can boot the recovery console from the windows disk (you haven't got) or from the boot menu if you installed it with 'winnt32 /cmdcons' - you didn't so you need a disk.
If that fails you will need to do an inplace install which will correct the hardware problem which you may have inadvertantly introduced when you changed your motherboard.