I have a Athon +1700 Socket A L7S7A2 mother board with AMI BIOS.  My house has been recently struck by lightning BUT my computer was unplugged and was largely uneffected.  As soon as I TURNED it on HOWEVER there was no sound, just beeps from the CPU instead.  I thought I could fix the problem by WIPING the harddrive (which I was planning to do before the strom).  When I reinstalled windows, everything worked fine but instead of my computer reconizing that there was a sound card there and all it had to do was FIND a driver, but that didn't happen.  The sound card was never recongnized the computer doesnt think theres one actually there.  This has never happened before, it always shows up on device manager and then it finds a driver for the hardware.  I would apperciate any suggestionsDo your speakers have their own power cord?  Were they plugged into the power outlet during the storm?  If so, I wonder whether your sound card may have been damaged via a charge of electricity passing through the speakers into your sound card.   Do you actually have a sound card or are you using onboard sound?

You said your computer was "largely uneffected"?  Have you noticed any other problems since the electrical storm?the router and montior got fried, but come to think of it they were plugged into a surge portector, plus the mouse got fried as well.  Which is kind of strange.  I believe I have on board sound. Yes the speakers were plugged into the wall, I suppose the card got shocked as well then  :-/Wow, you really got hit!  Are you using that computer now?  Again, does it seem to be running OK except for sound?  I'd say there's a good chance your onboard sound was damaged by the hit.  Might just double check your speaker connections and your sound settings to be sure Mute is not on.  You might also access your BIOS and CONFIRM that onboard sound is not disabled; obviously, it should not be if you've been using onboard sound, but, after such an electrical hit, I think I'd check there, also.  

Then, if you still have no sound and your computer appears to be functioning OK otherwise, I suggest you get a sound card and install in a PCI slot.  Here's an inexpensive one: CHAINTECH AV-512 Sound Card - Retail.  I've been using this card in my system for a year or so and have been quite satisfied with it. Quote

struck by lightning BUT my computer was unplugged and was largely uneffected.

No I don't believe it was partly damaged because then the whole motherboard should be out of commission as well.