added 2gb 4200/533 memory, shows 3200/288?

I upgraded my memory on my IMac G5 isight (2006 model) from 1gb to 2.5 gb by changing the 512 memory to a 2 gb card. The new card specs were 2gb DDR2 PC5300/4200, 667/533MHz (the IMac specs call for a PC2-4200/533). My IMac shows 2gb 3200u 288. I returned the card to the store and exchanged it for another with the same result. The label says GB Micro which is, I believe, a reseller that uses more than one manufacturer. The tech at the store says this memory has an excellent track record for them (I believe them). If anyone has any insight, advice, or ideas about what is happening I would love to hear them. Thanks.

Even with the correct DDR 2 modules there are all sorts of variants - ECC; non ECC; ECC Dual Registered etc etc.

This is the type of modules you need. Sounds like you have purchased from a PC shop:-

512MB PC4200 DDR2 533MHz 240 Pin DIMM... (OWC4200DDR2M512) at OWC

Thanks Harry, OWC has a great website. From reading the posts I thought memory was generic; is this incorrect?

Sure is. Remember most forums (other than here) are nearly PC exclusive.