Change drive letter for CD drive on Windows 7
Solution 1:
Right click on the Computer icon on the Desktop and select Manage option.
Select Storage > Disk Management or just run diskmgmt.msc (administrative rights needed).
Right click on the CD/DVD icon in the bottom panel and select Change Drive Letter and Paths...
Change the letter and select OK.
In some cases, for the drive's entry to show up in Disk Management, it has to have a readable CD/DVD inserted.