I bought an new PC a week ago and the DVD RW Drive in it reads burned DVD's as blank.I cannot read the DVD's burned in the same drive.It can read factory DVD's like Vista Ultimate
Original DVD.But it shows up burned DVD-R as blank.

UPDATE:It can read DVD+R discs fine but when I put a DVD-R disc it shows the disc as blank dvd.

try going to device manager,then reinstall the driver for your dvd drive