You can change it from the Disk Management snap-in for MMC. Go to Start -> Run and type in compmgmt.msc, then look under the Storage drop-down for Disk Management. In here you can right-click on your CD drive's entry and select "Change Drive Letter and Paths", then proceed from there.
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Laptop: Turion 64 X2 @ 2GHz, 2GB DDR2-667, 100GB HD, ATI Radeon X300, 15" LCD, Seven Professional RTM