What's written on the PC is useless... just points out that's XP compatible...
I usually use partition magic for partition resizing, but you have the choice...
Anyway cut about 4.5 Gb from your older win partition and leave it there...
Start installing RH9, when asked go for manual partitioning with DiskDruid.
From there you must at least make a swap partition and a (ext2/)ext3 partition. I usually keep 512 MB for swap and the rest for ext3, obviously you have the choice.
If you want to access your other partition from linux you'll have to tell him where to mount your other filesystem (supposing that's FAT32, NTFS isn't supported without some tweaking). Double click on your win partition (FAT32) and tell him to mount it @ "/mnt/win_c" or where you prefer.
The rest is quite intuitive, so just give it a try and you'll see that's easier than expected...