Many people heare a re ready yo help you.
But first
What video card did you have before?
Did you really do the install the way they said to do it?
Does the manual say the you must set the VGA back to plain VGA first, before you power down remove the old card?
Many hardware devices, especially graphics cards, are very picky, picky sabot the exact sequence of things you do with the installation.
If you mess up the system, you may have to put the old card back in and reboot in last good configuration.
So, did you put the old card in and get back to good configuration in safe mode?