Kdenlive is reported to work on recent computers, with at least:
Any computer produced after 2005 should meet these requirements. You may only need a firewire interface.
For advanced use and semi-professional work, we recommend investing in a recent computer with:
In december 2008, some European retailers offered this kind of hardware for 500€, with one large screen. This is at least 4 times less than the equivalent under other operating systems. Don't spend your money in software licences for closed environment: buy camcorders and make films.