classpnp.sys - scsi class system driver
normally runs alongside storport.sys to run your storage drives
I suspect fix is to replace a driver. I don't know what you have though.
Can you download and run Driverview -
http://www.nirsoft.net/utils/driverview.html
All it does is looks at drivers installed; it won't install any (this is intentional as 3rd party driver updaters often get it wrong)
When you run it,
go into view tab and set it to hide all Microsoft drivers, will make list shorter.
Can you take a screenshot from (and including)Driver name to (and including)Creation date.
upload it to an image sharing website and show link here
crackling noise could be you need to update audio drivers. they are one cause of DPC latency, as are LAN drivers