Anthony,
The Adaptec 2100 Card should have a utility that you can access after the
bios that will allow you to configure the RAID 5 <ctrl-A>.  If it was
previously in a RAID 5 configuration with the same drives in the same order,
you should not have to do any thing but repartition it.  You will need the
driver for the Adaptec card for your Linux OS distribution.  The OS does not
know that it is using a raid, everything is handled by the card.  You will
also want install the Storage Manager so that you will get an alarm if a
drive goes bad.  I use that card on an old NT box and it works well though
the Storage Manager is not as good as the one that comes with the AAA-131U2.

http://www.adaptec.com/worldwide/support/drivers_by_product.html?sess=no&cat
=/Product/ASR-2100S

Good Luck!

Gilbert