What you have there is a hard disk drive. In order to fit it into the CD drive (or Compact Disk drive) you need to first compact it! A hydraulic press is the preferred method.

Too big, use this:

You have to sand it down to fit. Easy mistake to make

Have you tried pushing it really hard?

In all seriousness, I've always thought the platters were extremely thin inside a HDD, but never actually had one open. That looks quite thick actually.

It's a common misconception to try this in the cd drive. You actually have to insert it in floppy drive slot (nowadays only really old computers have them). You might have to push it in with a bit of force though, because they tend to lock up if you haven't used them for a while...

You have to use toothpaste (if I remember correctly).

They make really good spin fidgets.

Did you try microwaving the CD?

You goof, you need to put it into the floopy drive!

That's a mirror sir

They make excellent coasters and those magnets ensure things will NEVER fall down

Weird, try blowing on it

That’s a drinks coaster.

Putting it in the freezer might shrink it down a bit.

Use a hammer.

Put it back into its CD drive, the one on the table that you took apart for no reason at all, and it’ll work a treat, I promise.

Seems you accidentally made the inner hole too big, just make it smaller with some duct tape and you should be good

Because it's the wrong size

Because they are prefab ninja stars.

put it in the freezer for a couple hours

Poka yoke?

You have to lick it to get it to stick to the laser.