I have just got a 4 port camera input card for my spare pc, £16.99 including software from ebay. I am intending to get a second card and fit the two, and use a large capacity hard disk in a hidden location to store all the footage. (I wonder if it's still called footage in these metric times!)
This together with the 6ft high driveway gates, using an £840 (just ordered) hydraulic radio controlled access system, and a 2m high fence with razor wire around my property should keep the **** out. The area has not been too bad, but things are getting worse, with this new homeless hostel being built on my doorstep not being something I'm looking forward to. I am also considering electric fence across the dividing section of my 2 pieces of land, and my existing infra-red sensors interfaced to my pc parallel port, with a VB program to record the events when the beam is broken.
I'm not going to make it easy for them to even get within touching distance of my assets!