First you need the RAID drivers on a floppy disk because Windows doesn't have them on the install CD so it needs them to "see" your RAID array which you create in the BIOS in the steps I mentioned above... in many cases it needs a driver for SATA HD's in non-RAID configurations too & either way (as I mentioned above) it'll need both the IDE & the RAID drivers installed to complete setup. *(note that some new motherboards will accept RAID drivers off of a CDR or a flash drive, check your manual to be sure)
The second question is a two-part answer ... first there are two types of RAID controller, hardware & software based. Software is really more like "hardware assisted" because the chipset does lay out the parameters for the array, but all management of the array is done in software & processed by the main cpu both in & outside of Windows ... this is the type found on most consumer motherboards including the 590-SLI.
Second, pure hardware controllers still need the driver loaded at Windows setup in many cases, because Windows won't automatically recognize the controller itself & as a result also will not "see" the HD's, however the RAID array is controlled by a seperate processer with software management interface only. In these "true RAID" arrays performance & reliability are greatly increased but so is cost, with the least expensive decent PCI-card models coming in around the price level of a low-end enthusiest motherboard, while high external arrays can run $15,000 or even more.