Spoiled few CDs while getting everything exactly as said in you guide, [R4A]Bigman.
I took *.sys and *.inf files from SATA floppy downloadable at Asrock home page.
Substituted the lines from viamraid.inf where necessary:
Viamraid.sys
%PCI\VEN_1106&DEV_3249.DeviceDesc% = viamraid , PCI\VEN_1106&DEV_3249
%PCI\VEN_1106&DEV_3149.DeviceDesc% = viamraid , PCI\VEN_1106&DEV_3149
%PCI\VEN_1106&DEV_3164.DeviceDesc% = viamraid , PCI\VEN_1106&DEV_3164
VIA VT6421 RAID Controller
First disk spoiled because I did not copy the first square bracket to Winnt.sif file.
Second was, I forgot to put Viamraid.sys in i386 directory.
Third coaster was because I left line in [SCSI.LOAD] section without ",4" part.
Forth CD finally WORKED
I used XP installation with integrated SP2.
The next step would be to integrate drivers into CMDCONS.