You're not doing it like it says on the kb, there's no point in repeating the procedure if it's not the one that is explained on the kb, it's also bad for us trying to help you that you say that you did according to the said procedure when you didn't, what you think that makes no difference in fact it makes a lot. The 'above exception' makes ALL the difference (you're downgrading XP to sp1 everytime you do a repair install with the xp sp1 cd).
If you don't use a slipstreamed xp with sp3 and you've downgraded to sp1 (also note that bootcamp is supposed to be installed with xp with sp2 not sp1, that's Apple's recommendation), then the procedure in the kb doesn't apply to you. You should do this instead:
Install Bootcamp latest patch, boot into Parallels and install Parallels Tools, boot back into boot camp and upgrade to SP3. You might need to install SP2 before Bootcamp drivers, thou, I don't know what are the exact incompatibilities with SP1, but Apple clearly recommends XP SP2.
So, in this situation you should, prior to SP3, update BootCamp, update Parallels Tools. And if that doesn't work. You probably have to update to SP2 prior to all that.
So, there you have it, there are more than one reason why it's not working, no slipstreamed sp3, you used Windows XP SP1 cd, and you didn't install Parallels Tools 5608 in the Guest prior to upgrade to SP3.