Wanting to spend the winter in the US

Thank you so much, Reba. I'll treasure your advice!
In 2004, I entered the US by car and left by plane. Nobody asked me anything at the airport when leaving the US for how long I stayed in the US or if I overstayed, for that matter, therefore I do not have any stamp of "entry-departure" record on my Canadian passport from the US authorities. (I had one on my previous passport).
In case I am asked about my two entry denials this September - question to which I'd answer truthfully - should I also tell them that I visited US in 2004 after my denial entries? Would that be favorable to the new situation by giving me some moral credit?
Much obliged...

"One month later, I succeeded to cross the border by car and the border agent did not ask me a thing! My crossing in and out was not registered, which probably means that I cannot prove that I traveled to US once and did return after being denied entry twice. I did not know until today after reading on this wonderful website that I could have requested a I-94 (is this a visa?)."

Your crosings are ALWAYS registered in the sytem. The fact that you were let in, shows that the Officer used his own deductions to determine that you were not an intending immigrant. We will not give you an I-94 unless there is a reason for you to have one. Your previous refusals will always be seen by all officers no matter where you cross. Just be honest and Reba's advice is right on.

Thank you so much for your help, lawsrlaws! I thought that my crossing into US was not recorded at POE in 2004, because the border agent was not sitting at a computer. When I flew to US or tried to enter by bus, the border agents were in front of computers which they used when checking the passport.

LOL, there are still a couple of ports like that. I believe they still would have recorded your plate, but who knows. Anyways, good luck and enjoy the sunshine.

The border agent stayed by the car all the time, was very polite and all smiles. He asked our names, purpose and length of trip. My friends' passports were even expired! He looked inside the trunk, as well. Then he wished us "Have a pleasant trip!" It took about 2 minutes all the inspection. Unless the agent had an excellent photographic memory, which is hard to believe, don't see how he would have managed to record our passport info.
Cheers!