OK well as you recall my ram chips weren't working in harmony.
I had 4 g and wanted to add another 4. Four chips dual channel.
Gateway FX series Win 7 64 bit.
The two new work fine and the two old work fine.
Put em together and whaddya goy?
 
Anyhow it seems one set was from a 2007 batch so I ordered four new ones from the same batch.
We shall see how that goes.
 
If that won't work they say they'll take all the newer ones back no problem.
 
Stay tuned.
Cheers
WSS

Were the two new ones the same as the old, or a different type/part number?   If you use "unmatched" memory the speed will be the speed of the slowest memory. 

When I did user support at Dell, we found not all non-Dell memory worked in a Dell. Some brands would not work or were iffy. 

I don't know what memory you used, but run the configuration on a site such as Crucial Memory and it will list what memory is compatible for your specific PC model.

Yeah I used the Crucial app when I ordered the pair.
It looked like the specs and speed were the same as the old pair but just to be certain I ordered four sticks from the same lot.
If they don't work I'll give up and live with 4 gig until I get a new machine.

I reset the BIOS using your battery removal method.

WSS

Usually, Crucial works without problems.  When I did user support on the Dell forums, Crucial is what I and all the other techies would reccomend for non-Dell memory since Crucial guaranteed their memory to work.

The battery reset method is what Intel (and many other vendors) reccomend to fully reset the BIOS (CMOS Memory).  Some say take out the battery for 10 minutes, Intel says 15 minutes.

I had a system yesterday that I had to use the "battery reset" on.  It was having problems and I reset the BIOS with the BIOS reset switch on the motherboard but was still having problems.  I did the battery reset and it fixed the problem.

Well good news.
Crucial sent me four new chips from the same lot. Put em in and bingo.

Cheers
WSS