DualBoot has some tricky points, when using an IDE RAID device as boot media, but as far as i know, it's possible with the real 32bit windows OS. (but not the older ones like w95,w98,wme)
but in the end, to set up redhat9 on such a device is pretty easy.
0) create the HPT372 driver disc, as described in the Highpoint documentation.
1) put the redhat dics1 in cd-rom and boot up from it.
2) at the prompt before the very start of the redhat installation enter:
linux text expert hde=noprobe hdf=noprobe hdg=noprobe hdh=noprobe
(the "text" you can leave away, if you'd like to install rh9 in graphical mode)
3) press enter and follow the instruction, when it comes to the driver disc.
4) if everything is correct you'll see something like "hpt....." as drivename in the partition manager, instead of the real drivername of your harddisks (like ibm...., or maxtor...)
If you see two drives or the real name of your disks, then something went wrong and you should stop your installation.
5) make your partitions as desired (auto make is not recommended
6) when it comes to the Boot loader, click the Advanced thing and go on. On the next screen you have to enter the following in the field:
hde=noprobe hdf=noprobe hdg=noprobe hdh=noprobe
7) also somwhere here, you'll see a little hint abouth dualboot..please read it and make sure that it works with your OS and also select the correct place for your boot partition. (MBR)
8) now you can finish the installation as normal, thanks to the built-in support for HPT372 chipset.