A computer usually only makes noise from a few places
1) The speakers (*evil grin*)
2) The Fans
3) The optical Drives
4) The hard disk (rarely loudly)
If its the speakers, then your daughter simply needs to exit whatever program it is that is making the noise (if its antivirus/antimalware then she needs to take care of whatever its complaining about)
If its the fans, a clean-out of the dirt may help, but noisy fans should be replaced.
An optical drive could make noise because of a badly shaped CD or DVD, or because its screwed in too tightly or too loosely (can be further reduced with rubber mounting kits)
If a hard drive is making a loud noise, then panic, its about to (or already has) fail(ed)