Hi,
You can likely play CDs on a CDrom due to the fact there is a small cable running straight from your CD player to the sound card. It bypasses much of the software you'd need to get it there through the bus.
Specifically the sound card's drivers...
I'd say you need to simply update/install drivers for the sound card.
Check out the sound card's manufacturer's website or
http://www.driverguide.com/
To install them once you've downloaded them, follow the instructions that maycome with them or...
Right-click my computer, choose properties.
Select device manager tab.
The sound card will possibly have a yellow ! point next to it...
Click on it. Or find it if it doesn't.
Click properties, select the driver tab.
Choose update driver.
Browse to the driver files you downloaded and select the .inf file
Let it do its thing...
Hope this helps.
Cheers,
Tim.