Difficulty 1 hashes are found all the time, and the only use is to send to the pool to prove that you're mining (they're really easy to check, but hard to generate). The same work that's looking for hashes of the current "real" difficulty generates those low-difficulty hashes as a by-product. Mining pools call them shares.

When you stop guiminer, the progress isn't lost, it's saved (as the number of shares you've sent so far). The pool settings determine where the payouts are sent (and what the threshold is).