Editing HD Video from the Canon 5D Mark II

I've bitten the bullet and bought a new PC to allow me to properly edit the High Definition (HD 1080p) video from the Canon 5D mark 2 camera. My current setup is more than adequate for photo editing work as I have dual core processor and 4Gb of RAM but this just isn't enough for HD video. The recommended minimum spec is Quad Core with 3Gb of RAM so my new PC will be substantially better spec than that.

As a separate issue it appears that there is a known problem with playing the HD video from the Canon 5DII using Apple QuickTime on a PC running Windows XP. The frame rate is very jerky with dropped frames which doesn't happen with Canon ZoomBrowser EX software.

The specification of the new PC is

Intel Core 2 Quad Q6600 8Mb cache (2.4GHz) Processor
Asus Motherboard
ATI Radeon Sapphire HD3650 512Mb RAM Graphics card
16Gb RAM
3 x SATA hard drives
12 (!!) USB ports