make a temp dir near the root of C:
Open a command prompt
(Type xcopy /? for more info)
Code:
xcopy D:*.mobi c:\temp /S
replace the D: with the letter for your CD drive
replace the C:\temp with the path to the temp place to put the files
What the
slash S does is searches all the folders on the cd for *.mobi files
Once a CD has been done
Use Calibre add books from Directories (since you only have Mobi it does not matter)
Note that mobi may not exist on early CD's, use prc