Solution for csrss.exe at 100% CPU, plus dual-boot Vista warning

I get quite a bit from this forum, so I thought I'd take a moment to give something back.

This is a bit long, but I didn't want to leave out anything I did, in case that influenced the outcome.

I recently did an overhaul on my HTPC. The driving force was a failed ODD (HP DVD740i), but I took the opportunity to do a few things:
1) Changed the CPU (D 830) to a lower-power, faster model (D 940 - I know... but my Intel D955XBK MB doesn't take Core 2s ).
2) Tried to change the CPU cooler (thwarted by glue on the old XP90C cooler being too strong on the under-the-MB thingy)
3) Changed the ODD to a Lite-On
4) Because the Lite-On has a slightly different set of connector locations on the back (even though it is of identical depth), I had to switch GPUs to fit things back into the case, so I changed to an HIS IceQ HD 2600 XT. This change reduced power consumption, made the case internals cooler due to exhaust venting rather than mere circulation, and provided me with both an HDCP-compatible DVI output and DX-10 capability for future proofing.

So far so good. Fired up the HTPC, and it gave me the "you need to reactivate windows MCE due to HW changes" message. Fine. I didn't notice anything particularly disconcerting at that moment, but then again I wasn't looking...

Then I tried to install Windows Vista in a dual-boot configuration. I'd been using three RAID arrays: two (C: RAID 5 and T: RAID 0) on the Intel SATA device and one (F: RAID 0) on the secondary SATA device. I figured I'd just try out Vista on T:, leaving my primary O/S and boot drive (array) alone, to see if Vista would work well on the hardware. Nothing during the Vista install warned me that I couldn't do this, so I figured if it's possible why not try it?

First problem: Vista didn't finish the install properly. I think this was caused by the RAID arrays, though I thought I saw the Vista install copying the Intel Matrix Storage drivers. The install did it's first set of things, then rebooted and hung.

Second problem: I now had a non-working Vista install, and along the way it took with it my T: array. I believe that part of the install actually told one of the four drives in the T: array that it was no longer part of the array, because the C: RAID 5 array had a drive failure and the T: RAID 0 array failed due to loss of same drive (matrix).

Third problem: The Vista install changed the way Windows boots, so now the default behavior was to go into a non-working Vista install, or else I could manually choose the "older operating system" or whatever that boot selector screen now shows. Annoying.

Luckily, I managed to get into the old O/S on the remaining 3 drives in the RAID 5 array, and then run that boot selector restore application that you can find online (someone had posted about it on THG-F. Thank you!). I was then able to restore the two RAID arrays (C: and T to normal by adding back in the "failed" drive.

Windows did a checkdisk fix for itself, since T: had been messed up a bit, and was able to recover nearly all of the original data (nothing valuable - just recorded TV - but nice nonetheless).

So first word of warning: If you're planning to install Vista in a dual-boot scenario, watch out for problems with installing onto pre-existing RAID arrays. Simply put, mine didn't work when I tried that, and made a bit of a mess.

Then we come to the fourth problem: the system was running very hot and sluggish. A quick check on Task Manager showed csrss.exe running at 100% (well, 50% of a dual-core CPU anyway). I checked online and found a lot about potential worms and viruses if the file was located in an abnormal directory. I also read that deleting your user account would fix the problem if caused by a "corrupted user profile". None of this helped very much, and I wasn't too keen on sequentially deleting all of the user profiles on the system.

So it turns out that the solution to the csrss.exe problem was to stop the Windows service for the onboard sound! With that service turned on, csrss.exe runs full-tilt on a CPU core. Disable the service, and both temperature and CPU utilization go right back to where they're supposed to be. I believe there may be a conflict between the drivers for the audio on the new graphics card, and the drivers for the onboard audio on the MB.