Dell :: Studio XPS 1640 Sound Cracking/popping

I don't remember when it started but my sound cracks and pops when I play games (NBA 2K10, WoW...) and sometimes when I'm watching youtube videos. However, it's fine when I just play a song on iTunes. Well actually, it pops a bit when I first start the song, but then the popping disappears, which leads me to think that the problem is somehow related to CPU/GPU usage.

So I've been on the web for quite a while now trying to find solutions...and here's what I've tried:

1) Using headphones (sound pops in headphones as well)

2) Turning off the wireless adapter (sound still pops with wireless off)

3) Disabling all enhancements under "playback devices" (still pops)

4) Checking IDE ATA/ATAPI controllers for Ultra DMA mode (got 4 ATA Channels, ATA Channel 0 is in Ultra DMA Mode 6, ATA Channel 1 is in Ultra DMA Mode 5, ATA Channels 4 and 5 are not in any mode)

5) Updating IDT High Definition Audio driver (updated, still pops; read somewhere that rolling back the driver would solve the problem, but at that point I've already reinstalled a newer IDT HD audio driver, which means I can't roll back to the desired date...)

6) Tried using a different HD audio driver (tried downloading a realtek HD audio driver, but I guess realtek = IDT?? same problem occurred)

6a) Eventually found some HD audio driver for some HP laptop (driver is now called High Definition Audio Device (under device manager => sound, video and game controllers))(sound still pops)

Specs:
OS: Windows 7 Home Premium 32-bit (6.1, Build 7600)
Processor: Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40Ghz (2 CPUs), ~2.4Ghz
Memory: 4096RAM
Graphics: ATI Mobility Radeon HD 4670
Bought: Around July/August 2009