After repairing WinXP to SiI3112 drivers under SATA RAID controller mode I can switch back the IDE mode in BIOS and SATA SiI drivers stay active. Hot swap functional :-) !!!
It probably means that If You don't need real RAID configuration (JBOD as single drive) only need SATA drivers (device listed in XP under SCSII) then it is probaly possible to install XP in IDE mode and just press F6 and insert drivers and that way makes XP use them. Those drivers have higher priority.
Maybe the mentioned change on Win2000 (djdiego71's recomendation in http://forum-en.msi.com/index.php?topic=86670.msg624029#msg624029
) on the fly just by updating drivers in properties if IDE device in Hardware device list is possible. Now I believe this.
Under IDE mode DOS programs and BootMagic works OK and WinXP uses SATA SiI2112 drivers with hot swap working. The only problem remaining is not functional Speedfan temeperature monitoring with those drivers instead of generic Microsoft IDE drivers. At the moment I am satisfied with the result :-)
Under SATA RAID mode BootMagic as well as DOS programs without loaded drivers for SiI3112 not working correctly :-(