Hello,
This white paper on the HP site may be of use to you:
In particular, see the section entitled, "Configuring RAID on non-factory preinstalled configurations," starting on page 12. Page 17 begins dealing with the OS image. If you have your factory restore disk, you should be able to do this. The RAID driver is available for download on the HP web site.
From the white paper:
"Before proceeding, you will need the following:
- Microsoft Windows OS media and Product Key.
- RAID driver UFD. To create, go to www.hp.com/support. Select your country and language, select Support and Drivers, click on Drivers and Software, enter the model number of the computer, and press Enter. "
I hope this helps.