No you can't but you can buy hd dvds that are two sided. One side has the hd part and the other side the standard.
like this one.
http://www.amazon.com/Breach-Combo-H...666351&sr=1-22
I've only had my hd dvd player for 2 weeks now but man does this thing take a LONGGG time for it to load a disc. The ps3 kicks it's ass.