Windows XP
eMachines computer with AMD Athlon processor

I have recenly bought a Cavalry 2x500GB external storage with built-in
RAID capability. I am new to RAID configurations, even though not for
computers in general.

Cavalry drive came with SteelVine Manager software that lets us
configure the drive in various configurations. Since my original
intent was to obtain 100% redundancy, I chose RAID 1 config and went
through the process. Now Windows recognizes the drive as one 500 GB
hard drive.

I have transferred a bunch of files (80 GB) to the external drive so
far.

My question is how do I know for a fact that the data is being written
to both the drives? I don't want to use Cavalry's software, but use
some external method to verify. Is there a way to verify this by using
Windows tools or any external (preferably free) utilities?

Thank you very much for your time.