My audio disappears after updating to snow leopard

So basically here goes. I bought a Macbook Pro off of ebay for pretty cheap, but unfortunately I didn't really know what I was getting into. It said as-is, sound isn't working but it does chime on boot-up. I thought it would be the elusive red-light fix in the audio jack but when I got it, no red light and no audio devices found in the preferences. I mean NO devices at ALL--input or output. I checked the midi thing and it shows the same, no compatible devices. I checked in 'About this Mac' under the hardware listing and it showed built in audio was present, the hardware ID is 0x83847680 which I believe is basically sigmatel STAC9221-A1 or something like that, but Intel calls it HD audio. The actual inputs and outputs listed are just the internal ones, but speakers and stuff didn't show up. It was like a truncated list. Whatever about all that though, here's where it gets juicy. I did a lot of reading and decided to just revert to OS leopard 10.5.1 (the retail release) and bam, audio came back. I was excited because I had been working on the issue for like a week straight and finally hearing sound was a relief. Then I updated it, anything past 10.5.1 breaks the sound and it shows once again 'no input' and 'no output' devices. I then decided to copy over my 10.5.1 AppleHDA and IOAudioFamily kexts, delete my extensions.mkext, repair disc permissions and reboot. This worked for updating to 10.5.2, sound came back. However, this doesn't work for Snow Leopard 10.6.3 (the retail box set I have). It shows no devices, and the kext trick doesn't work. Does anyone have this same issue or can give me any ideas to try? I did all the obvious things like zapping PRAM and resetting PMU and SMC crap, that stuff doesn't really help. I even tried deleting the device settings and system settings plist files. I also COMPLETELY disassembled the macbook pro to look for damage or loose connections. That was a total waste of time. It's perfect inside and out, I even put new thermal grease on. It's clearly not a hardware issue, but maybe lack of support issue in software??? I don't have the restore disc's that apple releases with this model so I can't do the hardware test or restore to Tiger. I can't even find these anywhere anyways. I have no ideas left from here.

Here are the specs on this machine:

Macbook Pro 1,1 15" A1150 (the ORIGINAL macbook pro, early 2006)

2gb of samsung ram

100 gb hdd

2.16 ghz processor

Every time I reboot, the boot chime works, however the only thing that I believe could be causing a problem is I always get a 'prohibited' sign right after the apple on the gray screen during boot-up. I checked the boot log and it says almost always complains about usb. Something about a controller being unloaded across sleep.

Any help?