new hard drive

i am new to macs, i have recently just switched over from pcs, so this could be a very basic question. My iBook, (1.2 ghz 1.25 GB ram, 30 GB HD) is rapidly running out of space and i am considering buying a new internal hard drive. i was wondering what kind of hard drives are compatible. i found a couple that i think are, and was wondering if someone could confirm which ones are and are not compatible with my iBook, thanks

http://www.powerbrixx.com/index.php?main_page=product_info&products_id=1246

http://www.vlp.com/index.php?main_page=product_info&products_id=1120

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=100809&prodlist=froogle

http://www.futurepowerpc.com/scripts/product.asp?PRDCODE=HDSA-NHM100JC&REFID=FR


i am leaning toward the 160 drive if it works cause it always good to go a little bigger,
thanks for the help