Dear mcube
Something similar to this was covered in a previous post a few months or more ago, do a search. The procedure outlined was fairly specific.
The general way to achieve this is to do a backup of your 40Gb drive to tape or desktop depending on how much data it has on it. Then remove the drive.
Then install the 2 x 100Gb drives and install the sme software in a RAID1 config. Then do a restore of your backup. Then load any additional rpms that were installed on the 40Gb drive.
Alternatively you can temporarily remove the 40Gb drive, then install the 2 x 100Gb drives and install the sme software in a RAID1 config. Install any other rpms you want/need that were on the 40Gb drive.
Then install the 40Gb drive as a third HDD although it will only appear as a second HDD, and copy any data from the 40Gb to the 100Gb RAID drive(s).
Hope this helps
Regards
Ray Mitchell