You need something to convert the signal from your camcorder into something the PC can understand plus software to capture and manipulate it.
Your PC may already have a capture card - so you can just plug in a cable from the camcorder and run the software supplied with the card to capture etc. More likely you will need to buy a capture card / device. the big names include Pinnacle, Dazzle, Hauppauge and Radeon (all in wonder / VIVO) - all the software you need will probably be supplied with the hardware.
A couple of issues ago PC Advisor ran an article that covered this and may help.