Gary Emerson wrote:
Ok, when I ordered my dell, I got twin 160 Gigabyte drives. I've had a
couple of drive failures over the last couple of years and when the
drives failed I found it very inexpensive to buy 300 and 400 Gigabyte
drives. However, the computer still sees only 160 Gigabytes of usable
space.

RAID 1 always limits your capacity to the smallest drive in the pair.
So, if you want to continue using RAID 1 and increase capacity, you'll
need to replace both drives. By the way, RAID 1 does a decent job of
protecting against hard drive failures, but it will not protect against
Windows screwups, operator error, etc. Backups are still a good idea...

Marc