I have a v5 (2001 edition)running windowsME, too. I tried and tried to install the sound drivers. The driver kept complaining that the sound was not enabled in the BIOS. There was no setting to enable sound that I could find.
BUT.... I re-installed winME and installed the video drivers first.
Then installed the sound drivers.
The I-O kept complaining that the sound wasn't enabled.
I gave up, and decided to just use the "silent" I-O anyway.
Then after about 5-10 re-boots--The thing decided that it wanted to work.
I am using a BIOS chip I got from BADFLASH.COM version 5.0.0.
I think that the reason I was having so much trouble was the fact that I installed winME on another machine, installed a bunch of software off of CD's, booted into safe mode, and deleted everything from device manager. Then installed the drive in the I-O. The sound and video are working great now though! Thanks for the tip!