Not sure what it is but it doesn't play back smoothly. I set the ASIO panel to the highest buffer, I don't know what else to do. I'm on a powerful new Dell Inspiron, with SSD. Thanks.

At least one common problem causing this on fast computers is that some process is stealing attention from the processor. A common issue is WiFi, which you can try to disable if you have it. For a more complete investigation download LatencyMon  http://www.resplendence.com/main
 

Thank you!

I wouldn't say a Intel core i5-3337U @1.80 GHz is particularly fast. It's fine as a business machine, but is probably around the minimum required for a DAW. Bear in mind that the "U" series processors only have 2 cores - unlike the desktop i5's, which have 4 cores.
 
I've got a Asus ROG GL552VW gaming laptop with an i7-6700HQ processor (4 cores, 8 threads) running at 2.6Ghz (with turbo at 3.4Ghz). I've yet to create a project that even comes near to maxing this out.
 
This only set me back £850 (around $1000 US) from Amazon, about a year ago.
 
If you find your laptop starts to struggle even after disabling things like the WiFi, then freezing the other tracks can help enormously.
 

Yr right...that's my old computer profile & I forgot to change it.
 

update - I realized that it only happens with one song...any idea why this might be? 

A plug-in in demo mode?

Run the free Resplendence Latency Mon, on the basic PC - not with Sonar running.  Latency mon should help in identifying the problems.  Run Latency Mon for a couple of minutes as the source of the problem may not show up on a short run.  And, as mentioned wi-fi is a know cause of many audio problems.
 
 
http://www.resplendence.com/latencymon
 
I bought a Dell laptop last year to use for off-site recordings.  It is an Inspiron 15 5577 which Dell sells as a "gaming" Laptop.  It has a 7th gen i5 and a 256GB M.2 SSD.  It is fast with the M.2 SSD, and loads and runs programs as fast (visually) as my DAW desktop machine that is an i7 6700K.  HOWEVER, no matter what I did to the PC I still had some dropouts.  The laptop had space to add a laptop size hard drive or a conventional SSD.  I had a spare SSD so I installed that and set up a dual boot with the original Dell disc image on the M.2 SSD.  I installed Win 10, needed device drivers, Sonar and the drivers for my recording interface, nothing else.  It runs clean with Latency Mon and also records without any problems.  If I want to use the laptop for regular PC operations I boot to the Dell M.2 SSD.  If I want to run Sonar I boot to the added SSD installation.

"A plug-in in demo mode?"
99 times out of 10 that's your answer...
 
T

thanks again for all the responses