More in hope than expectation...

Hello, all - quick question. Does anyone in/near Oxford have an old laptop I could borrow for a week or so? I'm off to teach a summer school for the Open University, and there's relatively little computer access. I'm to give a lecture about 3/4 of the way through, and it'd be nice if I could work on my lecture during the week. So if anyone has an old laptop (it just needs to be able to run Powerpoint) that I could borrow that would be lovely - failing that, does anyone know if there are rentable laptops available elsewhere?