As you know older pc's are not worth alot, it is hard to put a price on them really but id say computer 2 was worth the most, you could probably get £200-300 for it, the others maybe 200 ish.

Thats being realistic though, like if someone who knew about pc's wanted a cheap one just to surf the net etc, thats what they would pay, if some old granny wanted a pc they would pay more, bit like cars i guess.

If you want help sourcing some parts for a new pc just give me a pm