Unlike vinyl records, a CD Rom's information is read from the center of the CD until it reaches the outer edge. The data rings are circular and cannot be cut. A good rule of thumb is that for every millimeter you slice off of a CD you lose 7 MB of information. A traditional CD Rom holds 650MB of information, so if your presentation is only 25MB you can cut deep into the CD without corrupting any of the data.

Notice how the CD stabilizes on the outer ring and its balanced shape.

When shaped CDs first came out not much attention was paid to balancing the CD and the result was a CD that wobbled so much it was unreadable. Shaped CDs that balance on the outer ring normally need to be geometric patterns with at lease 3 contact points.