Way Way Off Topic.... but I am confident the knowledge base in thisgroup can likely help... Computer related

Ok, normally this is soaring, but I know there are a lot of really
capable computer folks who read this group and this item might actually
help some of the other folks out there in the future as well.

I have a Dell, set up with RAID 1. For those unaware, RAID 1 utilizes
two hard drives. The same data is simultaneously written to both hard
drives at the same time and is read from both hard drives at the same
time. The benefit of this is that should one drive "die" the second one
soldiers on and all you have to do is replace the dead drive and the
computer will automatically recreate a copy of the good drive and
therefore you have a full time backup.

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.

I'm hoping that someone can offer a suggestion on how I can upsize the
available storage to take advantage of the actual storage area on the
two drives.

While I have a couple of thoughts as how to do this, I'll stop here and
not taint a clean thought process for those who know this best.

Keep in mind that I am prepared to not only buy an additional 400 Gig
drive so that both drives are 400's (keeping the 300 as a backup) and
I'm also happy to go buy a large USB drive in case having a separate
external drive is useful in this process.

I'm down to only 10 Gigs of usable space on the 160Gig original format,
so I need to tackle this problem sooner rather than later. I also have
an older (don't have the version handy) copy of Norton Ghost.

It probably isn't important, but the drives are SATA. I do not know if
I have any way to add another drive to the motherboard. I kind of
suspect I don't.

Many thanks

Gary