Replacing RAM on Macbook Late 2007 3,1

I'm absolutely pulling my hair out (or what's left of it) over replacing the RAM on a friends old macbook 3,1 to turn into worthwhile media server.
I've followed these two guides, to a t, over and over again:

http://www.ifixit.com/Guide/MacBook+Core+2+Duo+RAM+Replacement/512

http://support.apple.com/kb/HT1651?viewlocale=en_US&locale=en_US

The macbook currently has 2 x 512MB ddr2 (what i believe is PC5300, 667 Mhz) modules in it - this is what it came with installed.

Initially I tried to put one 2GB ddr2 PC 6400 @ 800 Mhz in along side it and this didn't work (3 beeps, no startup chime)

I then put the two original ones back in and for a few tries I once again got either 1 beep & no chime or 3 beeps and no chime.

I then alternated the original ram and only put 1 module in and after swapping the slot I got it to boot with 512Mb.

My thinking at that point was that I had fried one of the original pieces of RAM (even though I have repeatedly been wearing an anti-static wriststrap).

A friend of mine then brought over an old Windows laptop and I tried the 2gb ddr2 in there, as well as the 512 that I believed was fried at this point and both of them worked straight away on his Windows machine.

I then kept reseating the original RAM and was able to get a boot with both sticks recognised, as normal for the machine.

I went back to the store and exchanged the pc6400 800 mhz today for two 1Gb ddr2 pc5300 667 Mhz modules and back I go.

I'm able to boot with the two original sticks of RAM yet if I put in either of the 1Gb modules in I get either 3 tones and no startup chime or 1 tone and no startup chime.

I really really think this is an issue with reseating the RAM as ocassionally when I put the original RAM in I still get errors, even though it is quite obviously working as I am currently staring at the machine fully booted up

Am I doing something blatantly incorrect or is this machine just too old to be taught a new trick??