help me out

hi all
this is a peculiar problem which i m facing from last 2 weeks.i have a 40 gb hdd..to this i added another hdd as a slave.my master was running XP pro.now after adding this,wenever i m trying to play a movie in Media Player(10)the following error pops up.Cannot play /close. Earlier i thought that it was d problem of CD but CDs which played earlier 2 r not being played.Can ny1 of u plz help me out on this and tell me exactly as 2 why this is happening and a solution to it!!!!!noder, i have observed discs which do not run in Media Player cannot b copied to HDD though u can run them in XIng etc. Can ny1 suggest a alternative to this!!!!!!
thnk u alll