It is your audio driver.. I used to experience this problem on a daily basis.. just remove your current drivers and try to find another set. Most times I found it occurred when the wrong driver was installed (wrong chipset drivers)
On my Dell what ever i got i reinstalled Windows Xp SP2
installed my Motorola sb5100 and then let it do some Automatic updates
well it did 101 updates 5 which failed restarted the computer. and some reason Windows SP3 wouldn't install .. So i keep trying to install RealTek 97 audio for computer well it almost finishes everytime but a big blue screen with Portcls.sys comes up
Ok come to find out what the deal is I Think ...
went to Services In Administrative Tools folder..
and my Human Interface Device Acess Driver is not working cannot be found...
GA-MA790X-UD4P running XP Pro x64 SP2. BSOD at end of boot sequence due to "missing portcls.sys". In my case cause turned out to be Realtek HD Audio (from Gigabyte) installing multiple copies of driver files in \WINDOWS\NLDRV\008
- alcxau0.inf, alcxau1.inf etc. Moved extra numbered copies to backup directory, problem appears to be solved!
Interestingly enough, I have a very similar problem with my Gigabyte GA-MA790FXT-UD5P-based desktop. Though in the directory you posted, I have viamrx64.inf and viprt.inf rather than the files you mentioned. It's also a Realtek HD onboard sound chip though.
I'm running XP64, and the BSOD comes up probably 50% of the time I restart the computer. The error mentions portcls.sys but doesn't say that it's missing.
Also, even though sound works, every time Windows logs me in and attempts to play the startup sound, I just get an "invalid audio stream" or something like that in an error dialog from Realtek HD. However, when I go to "Sounds and Audio Devices" and test the startup sound, it plays just fine.
I'm a bit disappointed in Gigabyte's audio drivers. It's kinda cool that I can plug my stereo system in however I want and the Gigabyte driver will ask me what I just plugged in (headphone, mic, left channel, right channel, surround, subwoofer, etc.) and dynamically assign the audio ports that way, but this BSOD problem and the startup sound issue does not reflect well on their quality control system. Also, it does get kinda annoying having to select "headphones" every time I plug the headphones into the headphones jack--I wish the Gigabyte drivers allowed you to "fix" the device assignment for the front audio jacks.