The ALSA driver replaces the OSS/Free driver. The OSS/Free driver is present in current Linux kernel (2.2). The 2.0 kernel are no longer supported. You could also take a look at Pre-Install, in case you would like familiarize yourself with steps prior to install.Also have a peek at Changes to know what is the current version, changes, additions etc.
You must compile the kernel with sound support , you do not need to select any of the other sound modules apart from sound support Before installing this driver, it will be helpful to read Modprobe carefully, the documentation for insmod, modprobe, kerneld/kmod and for the isapnp module if you have an ISA PnPsound card.
Running ALSA with 2.0.x kernels: Maybe you have an old, trusted box based on the old 2.0.x kernel series, and you do not feel like upgrading the entire system just to get some sound working. There is a good chance that you don't have to. But:
The compiling process is the same as with current drivers. Good luck.
You can only use ALSA drivers V. 0.3.x or older, because the later ones require the new kernel. They should still be available at the Alsa FTP Server
You must not compile any sound support into the kernel as opposed to current version, where the soundcore.o module is required.
You must bear in mind that not all the cards supported today are available in ALSA 0.3.x. There may be a chance of back porting some, but if you could do that, I think you wouldn't be reading this HOWTO :).
Remember that older kernel use kerneld to load/unload modules, whereas the current 2.2.x series has replaced it with kmod. So read "kerneld" for "kmod" throughout this document, and see the kerneld man page.
Please do not discuss v.0.3 issues on the ALSA-lists. Older versions are unmaintained and questions will probably be ignored.