In some cases your DVD drive may not be found by Windows 7, even if it’s visible in the BIOS and using the standard driver.
Try running REGEDIT, browse to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass, then delete both UpperFilters and LowerFilters in the right-hand pane (UpperFilters.bak and LowerFilters.bak entries can be ignored).
If this doesnot resolve the issue, resetting the drive letter has worked for some.
Click Start, type Disk Management and choose the “Create and format hard disk partitions” link.
If your optical drive is visible here then right-click it, select Change Drive Letter and Paths, click Change and choose a new letter.