IME if you're going through the gate with 2 items (laptop bag and disc bag), you'll be fine particularly if the laptop bag fits under the seat. Though a 17" laptop is pretty big and if you have an aisle seat where the underseat on some aircraft is narrower, it may not fit.

If you don't have status or a CC to get an earlier boarding group, you may want to consider buying Premier Access to board earlier in order to ensure you'll have overhead space.