I agree with Essex that WHS would probably be a good way to go. It is based on Win Server 2008r2 but has some nice simple setup tools so you can get shares, users etc up and running pretty easily. It is around US$50 from various places or whatever it is in the UK after being given a heavy slapping from VAT. It should be cheaper than Win7 Home Premium by a reasonable amount.
WHS comes with a backup program so you can configure that for backing up your important data.
Raid 5 is better left alone if you do not have a controller with cache and battery backup. Raid 1 for redundancy (2 drive minimum, loose half the usable space), raid 10 for redundancy and speed (4 drive minimum, loose half the usable space but gain speed over raid 1).
Motherboard raid is usually bootable where as Windows raid is not. Motherboard raid is suseptible to Bios updates causing problems including you loosing your array and all its data. If you never have a need to update your Bios then less of an issue. Motherboard raid may limit you to recovering on the same motherboard with the same bios if your motherboard fails or you may have array/Bios incompatibility issues.
Windows Raid is non-bootable, is transferable to any Win 7 / Server / XP (IIRC) system and you can access your data with a quick import of foreign disks. I personally find Window raid to be a easier solution for recovery as it is not tied to the hardware.
A hardware controller will give you the ability to add more hard drives and may have raid features. One very popular model is the IBM M1015 which is a cut down LSI 9240-8i (Raid 5 disabled without a feature key). It can be found quite cheaply on various auction sites as they tend to come as the stock controller in low end servers and the buyers take them out and replace them with better models selling the M1015s to get some cash back. The M1015 needs its Bios flashed in order to work with non-IBM machines. There are two types of flashing , IT - just a card for connecting hard drives or IR - Raid functions for Raid 0, Raid 1 and Raid 10. Flashing can be problematic as it only works on some motherboards. I have found the Sand Bridge (LGA1155) boards I have tried the flashing has failed. Using two old LGA775 board the flashing worked fine on both. Both the LGA775 boards were MSI but I do not know whether that has any bearing on it. Another option would be a LSI-1068e chipset based card. There are lots around and they are pretty cheap second hand. They only support SATA II (no big deal unless you are running all SATA III SSDs or adding more than 8 drives with expanders) but they are PCIe 1.0a. Because of this they only seem to work in PCIe 2.0 x4 slots and not in x8 or x16 ones. Most LGA775 boards should run them fine (PCIe 1.0a) but newer boards may have issues.
I would also agree with Petes suggestion on disk layout. User Windows backup for backup to an external USB drive (can take to another location in the event of some major issue with your office site), Raid 1 your data drives (Windows raid should be fine), Standalone boot drive and maybe have a spare drive around just in case. If the boot drive fails then put the spare drive in, reinstall and patch WHS and then import your array again. If you add a SAS/SATA controller card then you have a few more options.
RB
