Check out Other World Computing. I have bought RAM from them with no problem.
Much cheaper than Apple.
Apple is having timing problems posting ... I see someone else posted by can't see their post, so this may be duplicate information ....
The max your system can use is 3GB total in the two memory slots. You can install two 2GB memory cards, which will allow the system to run a little faster, however, it will still only access 3GB. When I priced memory recently at Crucial, a 2GB card was $26 while a 1GB card was $28. I've used Crucial memory for years in various systems, with no issues. http://www.crucial.com .
Memory is user upgradeable and this Apple note describes how to do that: http://support.apple.com/kb/HT1423#3 . Apple charges 2X for it's memory, which is manufactured by Samsung and others, so if you want to pay a premium, that's one way to upgrade.
While capable or running Lion, performance in 3GB may not be optimal (Lion minimum is 2GB and users are reporting better performance at 4GB).
To follow-up on your post a few days ago...why does my system only can access 3GB of memory? I swaped out an old 512 kb memory and replaced with a 2GB so the system is running 2.5 GB and I noticed considerably faster loading and application switching time. I am not a graphics intense user and certainly not a gamer, mostly use the iMac for writing and doing presentations, educational stuff. Thanks.
...why does my system only can access 3GB of memory?
It's either a limitation of the hardware or software architecture. Apple said the max is 2GB, however users and others discovered that it would support 3GB. Seems somewhat arbitrary, however, things do change over time.
Were you able to get your upgrade to work?
I have a mid-2007 IMac with two slots that are supposed to hold up 2 x 2GB. I have purchased the suggested memory (3x) and have been unable to get any of them to work. Everytime i must reinstall the original memory card to access my computer. Even when I put the original card back in and get the computer to boot up -- it doesnt recognize the additional 2GB in the other dock --- just the original 1GB.
I would really like to upgrade my memory so I can run the current operating system. However, i cannot do this without increasing the memory.
The cards I am putting in are:
2 x 2GB
Never heard of them. It's highly unlikely the quality will be up to requirements.
You need much more information about the specification, too - DDR2 covers a lot of different RAM specs.
Also there are two possible Mac models for 2007. The last of the all-white ones and the first of the aluminium ones.
The white one supports 3GB (1x 1GB and 1x 2GB, or 2x 2GB), the ally one 6GB (1x 2GB, 1x 4GB)
They both require 200-pin PC2-5300 (667MHz) DDR2 SO-DIMM modules.
I strongly advise you look at Crucial and OWC (links to them in previous posts).
Did you use the Crucial (memory) System Scanner? It is the tab next to the memory advisor (default start) tab. It takes only a few seconds to download and install it, then a few more seconds to run it and get the recommended results from Crucial. Everytime I have to order for a system that is where I go and it tells me what is installed and every possible option and cost to upgrade. It has never given me the wrong info.
And Crucial has a lifetime warranty. Apples are very picky about the RAM they will use. Crucial has never failed me with any Apple RAM upgrade.