In a laptop, check up online for your speaker set part number, any helpful sites showing disassembly, and think of getting the speakers and wiring off eBay, you may open up your unit to find the connecting point is damaged, even plastics can easily break, as you say, been dropped. I'd suspect physical issue/s.
I should say, my experience with Sony Vaio K series is extensive enough, a replacement mobo might be the best way to remedy it, Believe me, I did that process, the board cost me $25 on eBay, it was well within reason, and replaces any number of problems, now the palmrest is non working, a replacement is $11 to $15 in the low end on eBay, so all in all, that maybe the best solution, since Sony puts a lot on their mainboard, there are some connecting boards, a power outlet that's wired, so easily replaced, a powerboard to batt, etc, also off the mainboard.
Speakers, stereo, are on the power button trim panel, the one that leads entry into the laptop, between keyboard and screen, the 04 K series pulls straight up, once you fold the screen back. The speakers and panel have one flex cable to the mainboard
Example I Googled:
Your model on eBay is severely lacking items, but a pair of speakers ARE here, if ever need be;http://www.ebay.com/itm/Sony-Vaio-PCG-381M...#ht_2179wt_1058
I found a Non English site, sighting your system specs, sounds like what my Acer 4710 should be, a T7600 CPU is my intended upgrade, I had a T7200 IIRC, matched to a higher Intel Northbridge in the Compaq 6710b model, wouldn't mate to the Acer's 479m PGA
Different pins, that's a key in this processor range, the bus speeds tops out below 800Mhz
Having the graphics card is what I'm after on mine!http://0kazii.ro/laptop-sony-vaio-fz11z-in...vidia-8400m-gt/
Checked the specs, my 07 Acer 4710 is a near match really, same Wifi card I've got and using now! My Ram came as 512MB of DDR2, but upgraded to dual channel 1GB (2 at present) but my mobo allows 4GB max!! This post has been edited by Slamman on Friday, Mar 9 2012, 20:31