Sound stuttering problems as of recent.

Recently on playback of MP3's, videos, anything, the sound stutters every so often, the CPU usage can be at 0-1% when running foobar, or 1by1, or any other media player, and nothing else (nothing in the background anywhere) and still stutter, I don't understand it, before my sound worked fine, this is a new motherboard (approx 3 months old), its a Biostar NF61S Micro, using the onboard Realtek HD audio, Geforce 6600 PCI-express card, PCI 1x SATA RAID card (with 2 hd's running in raid0) and one sata drive single on the onboard nvidia sata controller (just going into detail here so people can help me figure it out) I'm running Windows XP x64 bit edition (I was running XP Pro 32bit for a while, didn't have the problem initially then it popped up just before I upgraded to x64).

I have no standard PCI cards installed, just my Geforce 6600 on the PCI-E x16 slot, and my SATA raid controller on the 1x slot, I'm using the onboard lan, I don't know why it stutters, but heres a list of things I've done so far to try and fix it:

I've defragmented my HDD, ran AV/Spyware checks, everythings clean, I disabled the onboard sound and I tried a different soundcard (albeit not a great soundcard, some cheap crystal soundcard that I had on hand, I do however know the card works as it works fine in other systems), I tried the soundcard in every PCI slot, no fix.

I also changed the DirectX acceleration on both the onboard and PCI card to try and fix it, still nothing.

I then rolled back using Acronis to an image of windows before the problem happened and back using my onboard sound, still didn't fix it, I rolled back again and tried with the PCI card, nothing. I even tried going back to a default install with just a plain copy of windows with just the sound drivers installed.

I just can't figure it out, and its driving me crazy, its not so bad anymore, but its still there, I've done all the obvious I can think of, driver updates, driver downgrades, everything, so any help would be greatly appreciated. Thanks for any help in advance.