I think you're not really understand what I want to do... Right now I have 2 hard drives... One is 10GB, the other is 15GB.
So right now it looks like this:
HD1 HD2
|------| |------|
I want to combine them to make one large linux partition
HD1&HD2
|---------------|
This can be done in windows quite easily using dynamic volumes and creating a spanned partition, but it seems more difficult in Linux because the only way I've found to do it is by using a RAID array.