Is my sound causing the BSOD's? (Blue Screen of Death)?

Im not sure but as far as I know XP 64bit is unstable..They say it has many bugs. But yes I guess from the name RTKHDA64.sys would sound to me as Realtek High-Def Audio_64.sys I guess. I recommend put your motherboard's CD in your optical drive and look for the audio driver and install it. Because your copy of XP probably installed the wrong drivers for the sound card in your motherboard. I would prefer to look for the driver that says for WinXP64 or WinXP64bit or whatever that is similar to that, if only if it is available in the motherboard's CD though. That should stop the BSODs