Well, here's what three Apple docs have to say about the matter as respects your particular iMac, and notice that not a one of them mentions any limitations:
iMac (Late 2006) - Technical Specifications1GB (2x512MB) 667MHz DDR2 SDRAM (PC2-5300), supports up to 3GB
iMac: Memory specifications and upgradesAlthough the iMac (Late 2006) computers will accept up to a 2 GB SO-DIMM in each of the two memory slots, the iMac will only support 3 GB total memory.
iMac: How to remove or install memoryThe computer will only use a maximum of 3 GB of RAM.
The only potential limitation I've run across deals with RAM interleaving, which,
if your iMac supports it (Edit: Doc #3 suggests that it does, and Mactracker says "
Yes".), will give you (what I believe is only) a minor speed boost:
1. Interleaving requires the same size DIMM in each of the two slots.
2. I've got no idea whether it works, even with matched DIMMs, with a Mac that doesn't recognize all the memory it's got.
3. Judging from your list of apps that you run, I'm not certain that you'd derive any particular benefit from it.
Edit: 4. Doc #3 also says: "
For best performance, fill both memory slots, installing an equal memory module in each slot", but, again, your situation is anomalous.
In a different vein, I see that you'll have some software updating to do...doesn't look particularly costly (to me) and that you're running some obsolete software, but what jumps out at me is that you're using AppleWorks, which may present a problem.
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I'm interested in using voice-recognition software.You may find
this thread helpful.