the driver you want is the emu10k1
. It is very well supported in the kernel. It is probably not loaded though.
It is weird that the only thing your friend did was add a kernel and the old one (which was not touched, right?) stops working correctly. This should not happen.
Since you managed to setup slackware on your own, I will assume you know a few basics. Feel free to ask questions whenever I assumed too much.
First things first. See, if the system recognizes your soundcard: cat /proc/pci | grep EMU10k1
. If this command outputs anything, the system recognizes your soundcard and there should be no need to reinstall a driver. Post back, if this is the case.
Here's another thing you can try. This will work, if the driver is present on your system, but is not loaded (this should be done by alsaconf automatically though). Its worth a try: modprobe emu10k1
(open a terminal, become root and issue the command)
If you just want to know, how to compile the driver, here's what option you need to enable in your kernel configuration.
Enable Device Drivers -> Sound -> Advanced Linux Sound Architecture -> PCI devices -> EMU10K1 (SB Live! & Audigy, E-mu APS)
and recompile the sucker.
(If you have no clue how to do that (after all, it's the holy grail of linux), speak after me: "Dude, what the f*** are you talking about?" and I will explain how to do it.)
Also, you might want to get your friend to fix what he just broke. ... Ahm, yeah, anyways, just a thought
Good luck with this information. Post back with any more questions,