Did you miss a typo? You cannot have an i5 and an i7 in the same machine. Could you mean a 15" laptop?
To go on, any fixes/enhances, stabilizing, alteration is going to force your machine to work harder. Pile up all those fixes one atop the other and many machines will struggle mightily.
Would you please attach your dxdiag for us to look at? It will help analyze the hardware and drivers of your machine. In the meantime do you have your PREFERENCES in PD set to activate your machine's available power? HP Envy Phoenix/4thGen i7-4770(4@3.4GHz~turbo>3.9)
Nvidia GTX 960(4GB)/16GB DDR3/
Canon Vixia HV30/HF-M40/HF-M41/HF-G20/Olympus E-PL5.
Tape capture using 6 VCR, TBC-1000, Elite BVP4+, Sony D8 camcorder with TBC.
https://www.facebook.com/BarryAFTT

That studdering is expected on that laptop. If the actual produced file is 1920x1080/p24 with a bitrate no greater than 28Mbps then that rendered file should play back smoothly on wmp, vlc, or the timeline of PD14.

The Dell Inspiron 15 7557 is a 2 year old laptop that can have either an i5 or 17 cpu. See this doc: http://www.dell.com/support/home/us/en/04/product-support/product/inspiron-15-7557-laptop/manuals .

There are the typos that Barry pointed out already.

Sorry but I'm new to all this. Its definitely an i7 processor, I don't know what dxdiag is and I don't know if the preferences in PD should be set to. Thanks.

Sorry, the laptop is a 7559 not 7.

See this sticky and supply part B: http://forum.cyberlink.com/forum/posts/list/45453.page . This is what Barry and others need to help you.

7559 and not 7557. That typo cause me to look up the wrong computer. Oh well...

NomadicBroos,
the dxdiag is pretty easy, you'll figure it out no problem, use the link. As for the PREFERENCES, first...
click on the GEAR thingy at the top top of your PowerDirector interface. That will open the Preferences dialogue.
Click on Hardware Acceleration tab and "tick" the boxes to activate them.
Now click on the PRODUCE tab and tick-on all those boxes. Some may be greyed-out and not available, depending on hardware, etc.
Also, in PREFERENCES, you can click on GENERAL, the top tab, and activate SHADOW FILES. Shadow files are lo-resolution copies of whatever Hi-resolution (HD) video media is in your project LIBRARY. When you activate the creation of those copies you will see, in your Library media, little yellow arrows on your HD clips. This indicates the shadow files are being created. It is recommended that you do not edit your project until all those yellow arrows turn GREEN. At this point you can begin to drag media into your project timeline.
To let you know, those shadow files being lo-resolution, will temporarily replace your original files, just for the task of editing. It is much easier for your computer to process lo-res files, especially after they have been fixed or altered with lighting, color, speed, FX, etc. When you are ready to PRODUCE your project, the computer will "magically" know to use the real original media files and retain the HD quality.
Read this post a few times, it'll be clear! I hate overlong posting... HP Envy Phoenix/4thGen i7-4770(4@3.4GHz~turbo>3.9)
Nvidia GTX 960(4GB)/16GB DDR3/
Canon Vixia HV30/HF-M40/HF-M41/HF-G20/Olympus E-PL5.
Tape capture using 6 VCR, TBC-1000, Elite BVP4+, Sony D8 camcorder with TBC.
https://www.facebook.com/BarryAFTT

Hi Barry, tomasc & NomadicBroos -

Damn! I was just going to cut loose with an overly long, unnecessarily circuitous post...

Maybe it's this one? http://www.notebookcheck.net/Dell-Inspiron-15-7559-Notebook-Review.154635.0.html That shows the basic specs anway.

Cheers - Tony
Visit PDtoots. PowerDirector Tutorials, tips, free resources & more. Subscribe!
Full linked Tutorial Catalog PDtoots happily supports fellow PowerDirector users!

And...I didn't even mention the PLAYBACK WINDOW PREVIEW QUALITY can be adjusted to increasingly crappier levels of resolution to reduce the strain on the system. NomadicBroos, the Preview quality control is under the Preview Window (of course), it looks like a square with a few lines in it and it is tucked between the camera icon and the audio icon. Preview Quality can only be adjusted if there is a media file (picture/photo/video) in a timeline. HP Envy Phoenix/4thGen i7-4770(4@3.4GHz~turbo>3.9)
Nvidia GTX 960(4GB)/16GB DDR3/
Canon Vixia HV30/HF-M40/HF-M41/HF-G20/Olympus E-PL5.
Tape capture using 6 VCR, TBC-1000, Elite BVP4+, Sony D8 camcorder with TBC.
https://www.facebook.com/BarryAFTT

I have a similar problem with the jumpiness of the preview which causes difficulty in judging exact timing for a cut - although the rendered version is fine. And I can accept that it's the low speed of my machine. However, changing the preview quality makes absolutely no difference to the jumpiness. The one thing that seems to reduce the jumpiness is when PDR has finished creating any shadow files. This releases some of the processing power back to the main programme.

Matt .
PDR14; Win10-x64; i7-6700; 3.4GHz; 16GB RAM; plenty of HDD space; AMD Radeon R5 330.

Hi guys, thank you all for your help. I think I've sorted things out. On closer inspection the playback in the preview window was ok. The jumping started after rendering. I noticed that the output was set to 1920x1080 25fps whereas my video was shot at 24 fps. I changed the frame rate of the render and everything seems perfect. Does this make sense ?