To allow Limited User's to burn CD's, click Start, Run and enter REGEDIT. Go to:
Look in the right pane for AllocateDASD and double click the entry. Set the value to 2.
On PRO, this is exposed in Local Security Policy under Security Settings\Local Policies\Security Options
"Devices: Allowed to format and eject removable media"
For XP Pro, you can do this by clicking Start, Run and entering SECPOL.MSC.
Go to Local Policies, Security Options, look in the right pane for Devices: Allowed to Format and eject removable media. Set this option to Administrators and Interactive Users.