OK, well given you have a P410i controller you're in luck, you can migrate from one RAID mode to another.
I would strongly urge you to backup your system first then all you need to do is either boot from the SmartStart CD that came with your system (you can always download a new copy from hp.com if you can't find it), once that's booted go into the HP Array Configuration Utility (ACU) and you'll be able to migrate using that.
Of course going from R1 to R5 will increase the available space on the array, this will need to be presented (again via ACU) to the OS as a new logical disk. This logical disk will then appear to Windows as a brand new disk, how you wish this to be used is entirely down to yourself of course.