|Look at the box- does it say "CD-ROM" or "DVD-ROM" in the black box in the corner?|
Open "My Computer," then look at your different CD drives. Are they labeled RW? DVD?
If the Sims 2 Double Deluxe disc you're using is a DVD-ROM and you don't have/aren't putting it in the DVD-ROM drive, then your computer won't be able to read it.
It may be something else, but try this. Might be it.
EDIT: Eek! Didn't mean to rate my own answer. Sorry.