basically, if you can get your hands on a 8-10GB HDD you'll be ok, if you want a faster system and are willing to spend a bit more, might suggest you go with profs suggestion, i have no idea how much hdds etc cost over there.
As for the problem, give it some time, might just be the page file afterall, if the hdds starts clucking and giving bad sectors, time for a new one asap.