DVDSP playing on a PC...

Real quick -
a client called me and states that the DVD I made does not work on his PC - now we all know some of our clients are not at all computer savvy...BUT, just am curious if I am overlooking something....
why would a DVD i made in DVDSP not play on a PC?
any advice or pointers are much appreciated!
ciao!

Was the DVD you burned a -R or a +R media? These media are completely different formats and depending on the DVD player in the PC, your choice may not work. Most computers and set top players made in the last 3 years can play both, but you need to know what hardware the client is using.