Alright... I was in that thread but now we have details. That's the way to do things.
You say you use an HP. So is this one of those prebuilt/preloaded dealies?
If so those are crammed with intrusive bloatware and Windows is usually set up in it's usual ridiculous way.
First thing to do is remove any and all bloatware from the system that you do not intend to use. Use a program called CCleaner to do this because much of that sutff can be extremely stubborn.
Second go into your Control Panel and get to the Power Mangament options (sorry... I have never used Win8 nor do I intend to. I am on 7 so you'll have to find this stuff on your own or ask the other members here).
You absolutely must set your power settings to Performance. You are likely on Balanced or Energy saver or whatever. This turns things on and off to save power but the this is NO good for any streaming data stuff like audio or video. More specifically you should go into your advanced settings and make sure your...
1) Hard and/or Solid State drives are Always On or set to max or whatever
2) Your USB ports are set to NEVER fall asleep
3) Your CPU and pretty much everything else is set to NEVER fall asleep
4) Windows is set to NEVER fall asleep or dim the screen or do ANYTHING without you telling it to do so.
You want everything going full blast at all times. If you use the system for other stuff and do not like that behavior then I think you can create a seperate user account for a more conservative power management setup but any time you are doing audio you want EVERYTHING awake and ready at ALL times.
Now let's take a look at your interface. PreSonus makes decent stuff. Not sure about your interface but hopefully it uses ASIO drivers. If not (read your manual to find out) then you shoudl think about investing in one that does. I recommend Focusrite products and personally use a Scarlett 18i6 which is rock solid.
Anyway... if your PreSonus has the option for ASIO be sure it is actually using the ASIO driver. You do this in Sonar's Edit > Preferences > Audio-Devices section.
Sonar works best in ASIO mode.
What antivirus are you using? Those prebuilt systems usually come with Mcaffee or Norton trials. They suck for audio and they kind of suck for AV too. You have to make a decision whether you want to use this system for general internet stuff AND audio or if you can use the system exclusively for audio. If it is the latter I recommend removing the pre installed AV and installing Microsoft Security Essentials. MSE is much less resource intensive and offers good protection. I have heard Win 8 uses Defender as an AV but I would really trust that.
Either way and no matter what AV you are using taking the system offline and disabling the antivirus' "Real Time Protection" will make things run a LOT smoother. However you can also simply add any and all Cakewalk and audio related files and programs to your AV's whitelist. People say this doesn't matter anymore but I notice a massive performance boost when I disable real time protection. I also do not use my DAW for any online stuff aside from snagging software updates so whatever... balance your performance and security needs accordingly.
You should also figure out what kind of hard drives you have. SSD (Solid State Drive) for you program drive is great. If the system has Hard Disk Drives though and they came preloaded you have to see how fast they are and hopefully they are not the dreaded "Green" drives.
Ideally you want at least 7200rpm drives. Green drives, even if they are fast, are designed to fall asleep to save energy and are not ideal for audio. If you find out your drives are low speed or green drives you should consider replacing them. As I said SSD drives are gonna work but are more expensive. For HDD replacements you'll wanna snag stuff like Barracudas or Caviar Black drives (do a google search to learn more about those).
Finally be sure to check your interface and disk drive buffer setting. You can check your interface buffers via the interface software (or sometimes via the ASIO panel button in Sonar Preferences but that isn't as reliable... better to ust figure out how to open your interface software). For recording you want low latency so you set the buffers low (if you expereince dropouts or crashes there are tricks within the project you can do such as freezing tracks but that bridge can be crossed later) and for EVERYTHING else such as editing, mixing, exporting or whatever you crank those buffers.
For you your hardrive buffers, in Sonar go to Edit > Preferences > Audio - Sync and Caching then increase your Record and Playback buffers (default is 256 IIRC... turn them up to 512 or more as needed).
You can keep an eye on your CPU, RAM and HDD usage by inserting the Performance Module into the Control Bar in Sonar. Look it up in the manual to see how it works (this post is already wicked long so... whatevs). That will show you what is being maxed out and give you an idea what you may need to tweak, freeze or simply not do.
There... tons of info for you. Get busy.
Also if you want more info on system optimization I personally used the Sweetwater System Optimization Guide (google it). There are a couple things in that that do not play nice with Sonar (file caching I think) but the tips about making hardware not fall asleep and disabling startup programs is gold.
Cheers and good liuck.