If you have a DV camcorder you may be able to dub the old tapes to MiniDV tape and simply firewire the lot into your PC.
IIRC some DV camcorders will also allow you to convert the analogue video signal to digital and send it to the PC via firewire in real time.
You plug the old camera into the DV cam and manually capture the footage in your fave PC program thus:
Old camcorder > S-video / L/R phono audio > DV camcorder > firewire cable > Computer
Check in your user's manual to dsee if this is possible and how to set up your equipment.
If you can't do either of those then you'll have to get a video capture card with analogue inputs (composite or s-video inputs are the most common).
Check out Pinnacle's website. www.pinnaclesys.com/
They do both home user and professional level cards.
Matrox and Canopus also do excellent capture cards (at a price) mostly aimed at the pro user / serious enthusiast.