Well, it looks from the files which you have already ported from the minidump file that you are having two issues. One is with portcls.sys which is related to your sound driver and the other is what appears to be memory corruption.
I would however focus (at this point) on the sound driver issue and make sure you have the latest or if you have the latest, maybe go back a rev or two (check release notes for specific fixes / problems).
Can you describe your system (MB, Memory, Video, Sound) and anything that you may have done in the beginning of October when the system became unstable? You can go to system restore and check to see if you loaded any new drivers in that timeframe as it usually creates a restore point as a result of installing the drivers.
I would also run a memory tester application (memtest86 or memtest86+) for several hours. While it is not a definitive test tool (doesn't always find problems), it is more reliable than not. I don't expect you to find a problem but you never know.
Does this BSOD occur when using a specific application (typically?) or is it random?
Also, if you have already done many of the things I have described, please let us know what you have done yourself to attempt to isolate the problem.
Thanks!
