My computer got set up for dual monitors

Hello,
I installed a new hp printer to my laptop and all of a sudden my computer thinks its' working on multiple monitors and is set for 800 x 600 pixels at 4 bit. I have tried going through the display properties to change it but it won't accept any changes. And, I don't know how to remove the second monitor. My computer has never been set up to have multiple monitors...so I don't know why it is now. First, how do I get the multiple monitors function removed and secondly, how can I make the computer accept the appropriate screen resolution and bit?