Well i figured it out. I'll post how just in case some other noob might be wondering.
* Dual boot Leopard / BT4 from internal HD on Macbook 3,1 - without DVD *
1) in os x install rEFIT with ext2/3 drivers selected
2) boot from a live cd (i used Mint 7) and use Unetbootin to install BT4 to external HD (usb) or usb stick.
3) Follow the instructions on Pendrivelinux for making a boot cd but change the ubcd/boot/grub/menu.lst to the one BT4 uses, or just use the one i made:
hxxp : // rap idshare . com /files/ 256491436/ usbcd. iso. html
4) Boot from CD, select the external usb, boot BT4
5) From there install BT4 to a previously made partition on the internal HD.
I'm sure there's better methods btw.