Innexpensive S-Video capture device for PowerBook.

Hey guys, hoping you can help me here. I have a 12" PowerBook. I'd like to get an inexpensive capture device for it, Firewire or USB. It would probably need to be svideo or composite at the least. I basically want to be able to hook the PowerBook up to my digital cable box occasionaly and have it record TV shows to the hard drive when I want one. I was at TigerDirect.ca and they have so many for like $60cad that are just a little usb dongle with the svideo cable attached but they all say they require Windows XP. The only ones I can find for mac are actual little boxes where you plug the cables into and they're like $150 and more. I thought macs were supposed to be video editing machines, yet I can't find hardly anything for them? Does anyone know if these USB ones really would only work on XP?? TigerDirect is mainly PCs so I don't know if they just don't say when it's for mac or what. I just liked the design of the little dongle things because it will only be once or twice a week I'd hook it up so just want something easy and something I can throw in a bag. Thanks!