You sign up to FreebieJeebies. You then try a free offer, say the 1&1 free trial. Now 1&1 awards FreebieJeebies a commission for you trying their service. This is what pays for your free laptop.
It works out for everybody. 1&1 now has one more person who has tried their service. FreebieJeebies profits from the commissions. You get a free laptop. Simple. :)