I used to do this - you should just need a video capture card, and then the relevant cables to go between your Sky+ box (red/white audio cables and yellow video cable) and your PC.
The capture card will come with software that will allow you to view and record the Sky box content - although it cannot access the hard-drive directly, it will basically just capture what's displayed on screen, so if you press the pause button on the Sky remote, the pause icon will display on the captured video.
Dunno if anyone's managed to come up with a way of accessing the video on the Sky+ hard drive yet - I presume it's encrypted and paired to the viewing card, so that could be pretty tricky.