I put this comment in the last step, but perhaps it should go here as well:
I had one (800MHz), that on the B&W power cable, it was so tight that it pulled the socket from the PC board. Never had that happen before, although the potential exists on many of them. Needless to say, that machine is now allocated as a parts unit. What I found is the safest way, and really not all that much trouble, is the remove the 5 screws, peel back the tape, and remove the speaker/switch units from the top cover. Worked for me, and avoided the risk mentioned above.
If you're doing this type of work, what's wonderful is to have a set of technicians magnetic drivers. I have a set of twelve that are about 6"long, and very skinny. Phillips 1, 0, 00, & 000 . . . Torx 6, 7, 8, 9, & 10 . . . and slotted 5/64", 3/32", & 1/8". I wish I could remember where I got them, but you could probably Google it. One of the smaller magnetic Phillips was perfect for removal AND replacing this screw. A word of CAUTION, though . . . probably best to keep any magnetic tools away from sensitive components on the PC board.
On mine (800MHz) there are 2 screws visible here, one of which is, indeed, just one of the optical drive case screws as you mentioned. But the other one was what it appears is mentioned here in Step 44.