My system (ancient intel Core duo with Realtek audio (Sux) was unusable for multimedia after I started connecting vpn. Didn't realize it was a windows update that hosed it.
Here's what I did to gain massive improvement.
Open the playback devices control properties. Choose your active output device and open the current device's, *in my case, speakers* properties, select the advanced tab, unchecked both check boxes regarding exclusive control of the device by individual applications and applications mode priorities. Save and close. This was outlined by Slayerxxxx earlier.
2. Open the power control panel, go to the "Control what your power buttons do," page and click the blue hyperlink for "Change Settings that are currently unavailable." Deselect the "TURN ON FAST Startup" check box, Save, shutdown (not reboot,) and start up again.
If you're on a laptop, you may need to play with your power savings settings and make certain that the powerscheme isn't timing out your audio I/o device
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I'm still getting an occasional stutter, but that probably is the VPN that's 800 miles away and clogged head end on my street. (Especially since School just got out.) I am so thrilled that I am no longer listening to the equivelant of terribly abused vinyl. The crackling before was awful. Hope this helps someone else out. Try it.