Dude! U seem to be all muddled up here......
Now to feed u in with some info.....
Not all Handycams allow transfer of videos through firewire, if they dont have compatible software/drivers along with the camera...........If urs does, great!!!
Using a TV Tuner Card will allow you to cature Video from any source(VCR, VCP, Cable, Handycam, etc.), without installing drivers for ur camera.........its the most flexible thing.
If ur handycam has an S-Video out, use that to capture the video, it gives really neat quality. you will need to connect the S-Video o/p of ur Cam to the S-Video i/p of the TV Tuner Card, and use a simple stereo cable for the audio. ( Or else use the normal RF cable)
Softwares, which you use to capture the video depend on ur end usage:
If you want to make VCDs, use WinDVR, PowerVCR, Pinnacle PCTV, etc.
If you intend to view captured content only on the comp, you can use Windows Movie Maker 2, Windows Media Encoder, iuVCR, etc.
Your last question is really weird....anyways...
Firewire, TV Tuner & Graphics cards are three different entities...though u do get a few TV Tuner Cards & Graphics cards in One(But i dont recommend them.....
Noticing the RAM u have mentioned, it suggests u dont have a graphics card, which inturn means ur gaming experience as of now, S U X!!!
If ur handycam supports Firewire transfer, buy a firewire card.
If u play games, buy a decent GFX
If u want to watch TV, Listen to FM on ur comp, capture video buy a TV Tuner card, Pinnacle is the best, Compro n Prolink are the other good ones.