HD Install :: Combining HD space into one mount?

I installed DSL to my friend's computer...
I'd like to combine her's HDs into one mount. (/home/dsl/files/)

For example:
/dev/hda1 mounted on / size around 300Mb
and /dev/hda2 + /dev/hdb1 mounted on /home/dsl/files/

What do I have to write to /etc/fstab?
I'd like more just to add few lines to /opt/bootlocal.sh.
Like this: mount -t ext2 /dev/hda1/ /home/dsl/files/.

I belive both HD's have to be formatted wiht same format eg. ext2 or ext3...

For short: I need to mount two or more partitions to same mount point.

Ok.
I searched the net...
And found this forum. This is getting really hard.
Should I take the challenge..? Hmm...

original here.