MacBook Pro (unibody alum. 2009) RAM issue

So I ordered 8GB of RAM for my macbook pro and installed it and got the three beeps that you get with faulty ram. Then I tried with one of the old 1GB ram chips and one of the new ones and it worked fine. Every arrangement (slots or ram sticks) works fine regardless of which stick or which slot as long as I have one of the old 1GB RAM sticks. Any ideas? I know this one's capable of running 8GB so I would really like to be able to.

According to Mactracker, your 2009 MBP can take:

8.0 GB
Memory Slots 2 - 204-pin PC3-8500 (1066 MHz) DDR3 SO-DIMM

I'm assuming you ordered 2 x 4 GB modules? And where did you order them from? We usually advise our members to order either from OWC or Crucial.

It sounds like you may have received mismatched modules which may be why they won't work together in your machine but will work with a 1 GB module in the other slot.

When you do that, what amount of memory does your machine show? It probably shows up as 4 GB rather than 5 GB?

No, it shows 5. It's SODIMM DDR3 1333mhz ram. yeah, 2x4. It's Kingston brand. Really good reviews.

You realize that you're using faster ram than your machine's memory bus is designed for? I would send both those modules back and get the correct memory. Macs are extremely fussy about using the exact memory it was designed for. That may be the reason you're having difficulty. Since it's showing up as 5 GB, the modules are OK but the incorrect speed may be what's causing the problem.