RAM

[TinStar]

ok. So my computer has 6 slots for ram which currently has 3 x 2gb ram. My operating system(windows 7 home premium) evidently will accept up to 16 gigs of ram so I decided to buy 8 more (2 x 4gb) but I was then informed that there may be issues with mixing ram sizes and things of that nature. I bought the exact same ram except the size. My motherboard has 6 slots and there is ram in slots 2,4 and 6. I was going to put the 4 gig ram in slots 1 and 3. Is this going to be ok? Should i just buy another 4 gb card? I have heard that it depends on the motherboard but I can't recall what the motherboard is other than that it has 6 slots and is a couple years old. (I'm at work...)

Thanks for your help!