The iMac uses DDR2 667MHz SO-DIMM modules, not exactly hard to find, but it’s the kind you use in notebooks, not desktops. However, Macs can be finicky so you might want to get some Mac certified memory just out the simple reason that the standard stuff might not work.
shopping.pchome.com.tw/?mod=stor … _NO=AGAD33
If that’s too expensive, then I’d go with brands that offer Apple upgrade modules if you want to chance it, so out of the ones on PCHome, I’d say Kingston or Patriot, don’t buy the really cheap stuff, as it’s more likely not to work, worst case. shopping.pchome.com.tw/?mod=stor … _NO=AGAD11