How is your drive partitioned already?
Can you safely reformat a partition as Linux?
Tip one: hard drive a is called hda
and drive b will be called hdb.
You can install Linux and Windows on hda as
hda1 and hda2.
Basically you format the section of the drive you want as Linux
and then create mount points.
The subdivisions of hda eg hda1, hda2, hda3
can be assigned mount point
hda1 /dos -- ie Do NOT reformat
oh yes and you need a swap space (twice your ram up to a Gig or so..)
hda4 could be swap....
Hope this helps.
I used to be tricky but if you go in as custom it shouldn't be too bad