You will need editing software. Pinnacle and
U-Lead are two reasonably priced ones.
Check if your graphics card can handle input/output of video. Graphics cards that can do this, I believe, usually come equipped with the necessary connection wiring (mine did anyway). If your camcorder is digital you will need a firewire connection. If it's analogue use the other connections to the graphics card. Hard drive must be fast enough to process the data, UDMA 5400 or 7200. As you have a 100gb h/d could make sense to partition this ( usually 2 h/d recommended) and use the partitioned area just for in/out and storage of the video data.