Mac Mini Memory upgrade issues...

I own a Mac Mini (late 2009) 2.26 gig core 2 duo. Yesterday, i bought a new ssd drive and a 4gb ddr3 1066 corsair laptop memory stick to install in it to get a performance boost. After installing everything, i powered my mini and got beeping noises in intervals of 3, with no picture to the monitor. I figured it was the memory rather than the ssd. i first put the 4gb corsair in bank 0 (the underside) and put one of the 1 gig sticks that originally came with the mini in bank 1 (upper dimm). after that, i put the original memory back in and it worked fine. I then took the original memory back out and just put the 4 gig stick in bank 0 (underside dimm) and got the same beeping noise as before. I then thought to put the 4 gig stick in the upper dim rather than the underside, and it finally read the ram and works. Now i was told that i could use any 8500 laptop memory in the mini, and that my model supported up to 8 gigs. Did it not work because the under dimm cannot read 4 gigs or because u must have bank 1 filled if that is the only stick in the mini? also, did it not work with the extra 1 gig stick because the memory are not exactly the same model? Any information is much appreciated. Thank you.