Hello and welcome to the forum,
To help you we'll need a lot more information about your laptop, windows version, film clip details - how produced / how put into the laptop. See here: Got a problem? Here's how best to ask for help.
Things you should definitely do:
- Update graphics and sound drivers, preferably from the manufacturers sites. Being a laptop you may have to update from Dell.
- install all windows updates.
- install latest version of QuickTime.
For your 'choppy clips' did you render preview files? - In timeline view if there are red lines across your footage, press [ENTER]. They will render and the red line becomes green.
Insanity is hereditary, you get it from your children
Welcome to the forum.
As Neale points out, there is much info that will help us help you.
The most important aspects will be:
1.) Your video Clips (full details here, please)
2.) Your Project Preset (needs to match your Clips perfectly)
3.) Your system's full specs. especially things like your I/O sub-system, i.e. your HDD's, their speed, free space, controller type and how you have them allocated.
The article that Neale linked to gives the reasons for needing that info, plus links on how to get it, if you do not know the full specs.
Good luck, and there is probably a good reason for the behavior, plus possibly some things that will help get everything smooth for you.