This is not really related specifically to the XPS M1730 since so many others with other systems have encountered this lately. I'm posting this for my fellow XPS M1730 owners who are experiencing this though in hopes this will correct the issue until such time as a patch or update is made available (don't hold your breath).
Symptom:Left 4 Dead will randomly freeze up and the audio goes into a very annoying loop @ time of freeze.
Drivers:Some people have reported success with Forceware 182.50 however I have tried 182.50 and all drivers after 185.66. You might ask why I did not roll back and try an earlier stock driver (such as the 179.xx Dell driver). The reason is simple... I prefer to take full advantage of 'The Beast' and run my 8800M GTXs in SLI mode. With SLI mode enabled, any driver prior to 185.66 will NOT support PowerMizer correctly and downclock the GPUs dynamically based on system load while on AC Power.
Valve has an article (last modified on 4/17/2008) on their support forums with info on freezes w/sound loops however this does not discuss multi-core support and the option of turning it off to correct it.
After reading this article I was shocked at all of the reasons they listed. Uninstall your Anti-Virus software? PCI latency timings? Disable audio? C'mon now Valve - let's be realistic.
After spending several days researching this issue I have finally pinned it down to Valve's shoddy implementation of Multi-Core CPU support. This has been a long standing issue with Valve's Source based games and was (I believe) first seen in Team Fortress 2/ Half-life 2. Regardless, this issue was well documented by users and testers of the L4D Demo and has been seen since the launch of the Left 4 Dead product. You would think Valve would've put it to bed by now and resolved it to make all of us multi-core owners happy.
In the end I found a post via Google on a forum (which I can't remember now) suggesting disabling multi-core cpu support. I did this via the in-game options menu and have not experienced a single crash. This has a downside to it though... I noticed a drop in FPS as a result. Everything else is ok but just seeing the dip in FPS kind of bothered me. Why can't this be fixed? Why can't I use the full power/capabilities of my CPU? Not cool Valve.
What's a bit odd about this whole situation is this... This is the FIRST time I have experienced freezes with audio looping. I had purchased Left 4 Dead at the time of the launch and have never had this happen before. Nothing has changed with my system configuration. The only thing which did change with L4D was the release of the L4D DLC update (4/21/2009). Something was altered in my opinion. To back this up, I have NEVER had issues with Team Fortress 2 with this laptop nor my previous Intel CoreDuo machine - and no, I did not disable multi-core support in the TF2 config file.
So, in the end, if you are starting to see freezes and audio loops with 'The Beast', you might want to disable multi-core cpu support in-game. Hopefully this will correct the issue for you... It did for me (at least I hope) :(