Laptops are often problematic . I cannot decipher the stuff you posted,, over my head, I use the simple DPCLAT test which I know is not as accurate, but at least it gives me a ballpark of what is going on... Red= Bad, Green = Good. 
If your experiencing DPCLAT issues, you need to deal with that first. Some Laptops cannot be tamed. Example, my laptop will not run audio until I disable the battery management in device manager. Wireless cards are also bad. 

I would try to record to the external drive. Nothing needs to be moved, just some config changes in SONAR

• "Project Files" in Project > File > Folder Locations and
• "Global Audio Folder" in Project > File > Audio Data

should be pointed to a directory on the external drive.
 
One thing to keep in mind when relocating the "Global Audio Folder" to removable media, if the drive is not available when SONAR starts up, the program will automatically revert the "Global Audio Folder" setting to "C:\Cakewalk Projects". It will not revert back to the external drive when it becomes available, it must be manually reset.

OK - let's back up a second.
 
You are using a laptop, which will have a Wi-Fi adapter present, which will FREQUENTLY cause massive latency spikes.  There is an easy fix for that, so do not despair, IF that is part of the problem.
 
Soooo, go into Device Manager, and just before launching Sonar, temporarily DISABLE your Wi-Fi adapter.  Do not worry, as you are not uninstalling it, it is only essentially making it invisible to Windows, and not really deleting it.
 
After you finish disabling it, you should see much better performance in Sonar, as far as dropouts are concerned, IF you have settings made reasonably well.
 
MY recommendation for a reasonable set of settings is as follows:
 
For your audio interface: Sample Rate of 48 k, ASIO Buffer Size of 128.  (If your interface uses a different term for it, you might have to tell it to adjust the number of samples or that sort of thing, in which case you want something like 200-230 samples).
 
For Sonar: Driver Mode of ASIO, Sample Rate of 48 k.  You want to shoot to end up with a Sonar-reported Total Roundtrip Latency of around 10 milliseconds or just a little less.  Please note that these settings are recommended for doing RECORDING, and not for doing Mixing/Mastering.  When mixing/mastering, you will need to likely bump up your ASIO Buffer Size to as high as 1024, which is fine, since you will not be doing tracking/recording at that point.
 
For the rest of time, you will be bouncing back and forth as needed, with your ASIO Buffer Size, as you move between tracking and mixing/mastering.  You need a low latency when recording, so you aren't trying to play through a giant lag, and that no longer applies once you move on to mixing and mastering, so the buffer can be really high.  This will accommodate plugins that are designed for the mixing process, which often use something called 'look-ahead processing', which will add LOTS of latency (it is scanning ahead to determine how to process, for effects such as Perfect Space or Boost 11).
 
SOOOOO, give the above a shot, and please post back and we will look at other things, as needed.  :)
 
Once you finish your Sonar session, by the way, you can enable the Wi-Fi adapter again.
 
You might consider also running LatencyMon with Sonar closed and the Wi-Fi adapter disabled, to see the difference that makes in your system's basic ability to handle streaming audio, such as what Sonar does.
 
Bob Bone
 

If the machine is not recording well at 44.1 what would be the benefit of changing the sample rate to 48?

I believe I've been correctly disabling wifi during each use of Sonar, but I'll give it a shot with the different settings suggestions, and if the problem persists I'll see if the external drive helps.
 
And by the way - thank you very much for all of the help, everyone!

44.1 k or 48 k - either one is fine.  I was too lazy last night to add 44.1 k, and additionally there is not much of a resource bump needed between one or the other of those, so why not go with 48 k?
 
But, again, you were correct that 44.1 k is also a fine choice.
 
I would hope that some local environmental issue is at work on this computer, causing the dropouts, because then we should be able to ferret it out.
 
Please DO list the Sonar-reported Total Roundtrip Latency value, from Edit>Preferences>Audio>Driver Settings, with the settings set to as I posted above (sample rate of either 44.1 or 48 k, ASIO Buffer Size of 128, Sonar Driver Mode of ASIO).
 
And, as Cactus posted above, I too had problems with the battery management devices in my gigging laptop, and I had to disable that stuff to avoid massive latency spikes.
 
Also, extra devices, such as COM 1 port, can be disabled, as it is a vestigial leftover for most folks, from way long ago.
 
I also agree that generally the whole background/foreground services tweak is not needed from Windows 7 on up.
 
Bob Bone
 
 

I was to lazy to copy paste this last night, But give it a try for what it's worth. It's free and take a few minutes to see whats up. 
 
http://www.thesycon.de/deu/latency_check.shtml
 
 

Off-the-shelf laptops are often problematic when used as a DAW.
Let me explain why (it's pretty logical when you break it down).
 
A typical laptop is designed for the "general purpose" end user.
That user is surfing the Internet, using Facebook, sending Email, running Office applications, maybe light photo editing, listening to MP3s, etc.  None of these tasks are particularly taxing.  The general-purpose user is much more concerned about battery-life than how well the machine sustains heavy loads in timing critical applications.
 
When you're dealing with ultra-tight space (small form-factor machines - which a laptop is an extreme example), performance compromises *have* to be made to keep temperature in check.
Notice that clock-speeds of mobile CPUs haven't gone up much the past ~5 years.
Power-management and CPU throttling help keep temps in check.
 
 
Off-the-shelf laptops often use motherboards where the majority of BIOS parameters have been blocked.  
This is done to keep tech-support issues to a minimum.
The general-purpose user will never notice DPC Latency spikes... or a 2ms hiccup in data flow.
When running ultra low-latency audio, those settings can make a huge difference.  
If there's a 2ms hiccup in data flow and your ASIO buffer size is 1.5ms, you're going to experience a drop-out.
There's not much you can do in this case.  The BIOS parameters you need aren't exposed.
 
All that said, some laptops are certainly better than others.
Custom built laptops tend to fair a lot better... as you at least have some control over the components used... and additional BIOS parameters are available.  Even with the best laptops, you're making performance compromise compared to a fast tower.
 
To summarize:
To effectively work at ultra low-latency, your machine needs to be able to (indefinitely) sustain heavy loads (processing and disk) without hiccups.
Those requirements are exactly the opposite of a general-purpose user.
 
 
 

Check:
http://www.intel.com/p/en_US/support/detect
 

Ok, so the round trip latency reported by Sonar is 101.9msec, 4495 samples. I've got sample rate set to 44.1kHz. Driver is set to ASIO. My ASIO panel (in Scarlett MixControl, with the Focusrite 18i20) only gives buffer size options in terms of msec 1-20, so the ASIO buffer size in MixControl is currently set to 20msec. Sonar says that ASIO buffer size is 20msec, 883 samples. The fast/safe buffer size slider in Sonar is faded and I am unable to move it. It's currently stuck all the way at the fast end. I wish I could share a screenshot of the page to make it clearer, but I don't have it posted at any url that I could pull it from.