yeah usually the sound keeps playing.
Ok... well there could be two causes of this that I've personally found, 1 is the multi core fix and 2 is the archive invalidated freeze. It's probably the archive invalidated freeze since you only have two cores to begin with... but give the first fix a try, and always backup your fallout.ini file before you edit it (very important).
1) Follow the direction in this article -> http://www.pdsys.org/blog/post/2009/02/07/Fallout-3-VideoDisplay-Freezes-sound-keeps-going.aspx, if you have questions about the article then private message me, or come back here and post your questions here.
2) If you use archive invalidated (most people do), then it very well could be the culprit. To test to see if this is the case, simply go into your fallout installation folder = c: program files/bethesda/fallout 3. Find archive invalidated exe, and run the program. When it pops up, hit deactivate. Then test the areas that cause the problems, if the problem is resolved then you have the culprit.... unfortunatly, this issue is as of yet unresolved. Quarn, the author of the mod cannot be reached as of late and his mailbox is full. So you're stuck trying to deactivate Archive invalidated, then going through cell, saving once you're through the trouble area, reactivate archive invalidated and continuing to play. It is not a solution, but it will get you through some of the trouble areas. Be warned, that it will cause some mods to malfunction, especially those whom are graphically oriented, such as Darn UI, weapon texture mods, and so on. You can follow the progress of this issue here -> http://www.gamesas.com/index.php?/topic/1173633-fallout-3-and-freezing-with-modern-cpus/page__st__20
To test these areas without having to reboot your computer after every freeze, go into your fallout 3 launcher menu. Hit the "Options" button, and put an X over the 'windowed' option under mode settings (bottom left hand corner of the options menu). That way, if it does freeze, you won't have to reboot. Just do a ctr+alt+del and click on fallout 3... and you know. Know that when you do switch it back to fullscreen, the resolution may be changed to something different, so adjust this to your preferred setting before continuing. Good luck.