Confused about disk space stats

I have 2 x 320 GB drives defined as a STRIPE array.  When I look at the usage stats, the system tells me that 123 GB are currently used.  While this does not really bother me per se, I was a bit started as I have not really installed much on the machine.

 

When I sum up everything on the drive, I get a grand total of around 62 GB (seems about right to me).  This includes all hidden and system files as well.

 

I could understand this if the raid array were defined as mirrored, but not with a striped array.  I thought a striped array did not actually waste any space as a result of the block (?) size.

 

I believe I have the latest mediashield drivers installed (XPS 710).

 

any ideas?  Am I missing or misunderstanding something?

 

thanks