Try to check kuno sa Disk Management kung nakabutang ba didto ang imong DVD-ROM. It is usually labeled as "CD-ROM 0". Basin ug drive/drive letter conflict.
Control Panel\All Control Panel Items\Administrative Tools\Disk Management
In the Disk Management tab, check if you're dvd-rom is listed. Right-click on it and click on "Change Drive Letter...". On the dialog box that pops-up, click on the "Remove" button.
Repeat this process again, but instead of the remove button, select "Add" and assign a different drive letter for your dvd-rom. Click OK.
I hope this helps.