How to soundcard from entering D3

I have an issue I've been trying desperately to figure out for the last two months. I can't find the power management options to stop my sound card from entering D3 while the computer is running. Basically, if no sound is playing for a period of time, approximately five minutes, the sound card switches from D0 to D3 and shuts down. Unfortunately, if any speakers are plugged in they start to hum. I can observe the switch in the "Power data" section of the driver details so I know it is the problem. Here is the contents of "Power data" if they help at all.

Code:

Current power state:
D0

Power capabilities:
00000089
PDCAP_D0_SUPPORTED
PDCAP_D3_SUPPORTED
PDCAP_WAKE_FROM_D3_SUPPORTED

Power state mappings:
S0 -> D0
S1 -> Unspecified
S2 -> Unspecified
S3 -> D3
S4 -> D3
S5 -> D3

The current state switches to D3 when the humming starts. Very annoying. There must be a way to edit the power management configuration on a per device basis but I can't seem to find any relevant information in my google searches. Any help would appreciated. Thanks.

HP Pavilion Laptop 2714ca
Built in sound card: Conexant High Definition SmartAudio 221

The laptop came loaded with Windows Vista originally but I wiped it the next day and used Windows XP for the past two years. No issues. Upgraded to Windows 7 Pro about two months ago, all of the drivers work fine except the sound card going to sleep because of the power management settings.