iMac G5 RAM - 4GB - so it seems that as well as the samsung M378T5263AZ3-CF7 1405 6400U PC2 DDR2 memory - that Sailor identified as working OK in an iMac G5 A1145

Also - Crucial CT51254AA667.M16FC 240-pin 1.8v Non-EEC 4GB DIMM PC2 DDR2 667MHz 5300 Desktop memory ?? - should work OK as well
Also - Kingston KVR667D2N5/4G 240-pin 1.8v Non-EEC DIMM PC2 DDR2 667MHz 5300 Desktop memory/RAM - does work OK - using it on my iMac now as I type this message.

Bear in mind that the Kingston KVR667D2N5K2/4G designation - CHECK for a "K2" which is added into the memory-ID if it is a KIT of 2 (TWO) memory sticks with a combined/added together (accumulated) memory amount of 4GB = 2GB x 2GB (per RAM stick). As these are NOT 4GB memory sticks.

CAUTION - the Kingston KVR667D2E5/4G is NOT COMPATIBLE with the iMac (or ANY Desktop system) as the "E" indicates it is ERROR-CORRECTED (SERVER) memory.

The "N" in the compatible memory (as above) indicates it is NON-ERROR-CORRECTED memory (Desktop (iMac) compatible).

I was supposed to be sent the Crucial memory stick (mentioned above), but the Kingston stick was delivered, and after cleaning - it then worked.

The strange thing is that when it is shown in the "About This Mac" in the mini MacOSX/hardware window it is shown as 4.5GB (0.5GB on-board memory and the 4GB memory stick), but in the more detailed hardware display of the "Memory" installed - the second memory slot is shown as EMPTY, even though the memory is recognised and works as it should. It seems some parts of the firmware cannot cope with displaying the extra memory, so it cannot display it in that section of the hardware details, as it was never expected to exist, or maybe that it would not be able to handle it, but it can!

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In my A1145 iMac 20" 2.1GHz system I too have had bad speaker sound, and it seems it probably relates to the thin rubber flexible border rim to the speaker cone becoming brittle/perishing and then it makes a bad vibrating/rattling sound instead of a nice clear pleasant audio response.

So, with my speakers that were affected I coated the rubber border with a glue called "Pritt Power Gel" (not sure if it is still manufactured) which is often used by paper crafters/hobby model makers, and that works nicely at bonding all the membrane together, while still remaining flexible and is not sticky once it has dried There are probably other glues that will do the same/better job, but you may have to search to find them, by trial/error.

It may work, though I have also replaced the speakers in another iMac with ones from an Intel (Core (2) Duo) based iMac (e.g. A1207) which can be picked up quite cheaply for parts and then the speakers can be "harvested" for the A1145 - if they are intact, though they may be worth coating with the adhesive/glue to protect them from any future deterioration!

Hope this information helps other MorphOS users with A1145/A1144 iMac systems.