nero express problem

hi
when i add tunes into the nero express from other web sites the time
lenths arent correct.if a tune is 3 minates than 2 more minates are
added by the express than it wont allow me to add more that 15 tunes
to a cd when there ususlly 25 tunes...has anyone had this problem and what did you do to fix it?im using nero 6 on xp.thanks

benbernie