PLEASE HELP lost 24bit true color display after using dell PC restore

My computer was running slow so I reformatted my computer using Dell PC restore.  It said it would restore the computer to the condition it was in from the manufacturer except now the resolution is bad and the true 24 bit color display is no longer available which was on the computer when i got it.  I paid for this feature and am frustrated that it is no longer there.  I tried updating the video driver but it did not work.  Please help