Can you check if they still showing in device manager?
Go to Start > Control Panel > System > Hardware tab > Device Manager
if there's yellow exclamation points next to the icons that means there's some problem with the device
I would probably guess you need to reinstall the drivers, so find a CD that came with computer and from device manager manu you can right click on each drive, select properties go to driver tab and select update driver, then just point it to the CD and it should find the drivers
if you don't see the devices in device manager, that means they aren't recognized or they aren't getting power