If they are school computers, accessing external storage devices may have been disabled deliberately to prevent unauthorised file transfers and virus-infection.
My college computers are like that. USB storage devices aren't recognised, and floppy drives are physically locked.
None of the computers have a CD burner.
The fact that all the computers won't read such devices means it's more likely to be an intentional restriction than a Windows or hardware fault.
The restriction can be set by using the "Group Policy Editor" in Windows XP Professional, or by a registry edit in other versions, the details of which I do not know.