Ive just been investigating the Intel Matrix Storage manager Utility (both ROM and in a windows xp environment apparently) and found this:
Building or buying a PC with a single Serial ATA hard drive, then upgrading to RAID at a later date is typically not a simple task, as it requires the reinstallation of the OS and applications. However, an Intel Express chipset with Intel Matrix Storage Technology** can be more easily upgraded to RAID capabilities when adding one or more additional Serial ATA hard drive(s). The Intel® Matrix Storage Manager software (included with platforms supporting Intel Matrix Storage Technology) handles the configuration and migration while running in the background, allowing users to surf the Web or read e-mail during the process. Once the migration is complete, dramatic increases in data protection or storage performance are available.
So I may well give it a go!