Check the Audio options in-game to see if any option is set too low or muted.Otherwise, use the setup program and try different sound driver options, especially with the latest/greatest sound cards, the (now 3 years old) auto-detect routines may not be entirely accurate with them.
If still have no success, write back with full hardware details, and see what we can do.
-----
Visit http://wiz8.web1000.com/ for a spreadsheet that allows you to enter in your spellcasters stats, and it will tell you what spells the character can learn, or for spells that they are not yet able to learn, it will tell you how many points they need, or why your character can't learn the spell.
Old mirror site @ http://wolfie.wiz8.de/