Since you're still in your OPT (F1 status), your previous paychecks will not count. Your H1-B doesn't start before Oct 1 07, so I don't see any option other than working for the current employer (the one who filed your H1) for at least one month. I am not an expert on this matter but the above statements holds true (friend's experience). But again, you might wanna talk to an immigration attorney.