Philips DVDR 1640 WON'T play normal dvd, but WILL play burned discs

I got a Philips DVDR 1640 a few weeks back. The burner works fine and
plays discs copied (burned) by itself. Trouble is, it won't play
retail discs. I have to use my old DVD ROM to play retail discs.
It's only by using the ROM that I've managed to read retail discs in
DVDShrink.

The machine is an Athlon XP 2400 with an Asrock K7S8XE mobo, 512mb
ram, and runs xp. The player is WinDVD4.

Any ideas?

thanks.

What region is you DVD set to? I don't use DVD Shrink, but it may remove the
region code (AnyDVD does), which is why you can view them through DVD
Shrink.

Also, try viewing through another player (if you don't have one, download
the trial version of Nero and use the Showtime program). Have you installed
any available WinDVD patches and have available codecs?

Fitz