iMac Not Booting Up After Installing RAM

I have a Mid-2007 20 inch iMac that has been running on 2GB of memory since I bought it. Recently I decided to upgrade the memory, and purhased 2x 2GB PC2-5300 667MHZ DDR2 Sdram from Amazon, which I am 99% certain is what I required (Apple's website doesn't sell memory for my desktop anymore, but a few months ago this is what it told me I needed).

Anyway, when I remove the 2x 1GB ram and replace it with the 2x 2GB ram, I hear the chime but there is no display whatsoever. So there are 3 possibilities in my mind:

1) what I purchased is faulty
2) I bought the wrong type of RAM
3) I'm an idiot and installed it wrong

Option 3 is least likely, because while I AM an idiot sometimes, I installed it exactly the same as I removed it. If anyone has any ideas or suggestions, I'd love to hear them. Thanks, guys.

Yeah, I've done that a few times already. Thankfully the 2x 1GB still works, i was just hoping to make it a bit faster.

WilliamG said:

Try the new sticks one at a time.

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This actually worked for me, thank you. I don't know why I didn't think of this on my own, but my system is already running much smoother with just 1GB more than before. Thanks again, everyone.

mojolicious said:

So have you established that one of the new chips is bad, or is it that your computer just won't accept both of them at the same time?

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It just didn't accept them both at the same time. Both chips work fine when installed one at a time.