Sound crackles in Windows 7, driver issue?

So here's the complete breakdown of my issue, and what I've done to troubleshoot my problem.

The sound that I'm recieving from the speakers begins to crackle and distort every other second or as the audio begins, on any file and even on start up, then it will play fine for about one or two seconds then crackle again.

Here is my PC hardware, it's a custom build. Just for possible software or hardware conflicts.

OS: Windows 7 Home Premium 64-bit
Motherboard: Asus P8Z68 Deluxe
Video: ATI Radeon HD 6870
Processor: Intil i5 2500k

I'm using the onboard audio, which is the Realtek HD Audio on the board.
My troubleshooting has led me to try different speakers, including my surround sound system, all of which came with the same results (crackling when any sound played). I've used my USB wireless headset as well for testing the audio and I have the same results, so this led to the conclusion that its a driver related issue (correct me if I'm wrong), however, I've tried multiple solutions to reinstall the drivers, including wiping my computer and starting from scratch with the Windows install disk.

Thank you.

***Update***
I've narrowed down what may be the problem, however it seems that the sound wants to crackle after some use (this is a theory) I just restarted the computer after uninstalling and reinstalling the drivers, it worked for the longest time then after a recent restart, this was due to Windows Update, so this leads me to the conclusion that some update has a conflict with the drivers.
 
Was Windows 7 the only operating system installed on this computer, or was Windows 7 installed over another version of Windows? Is Windows 7 Service Pack 1 installed?
 
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