One area you can upgrade is your memory. You will find the iMac will run much better with 4 GB or more. You can get more memory at crucial or kingston.
I purchased my iMac in 2006 and have never had any problems with it. It still runs fine for my purposes but I cannot use any new devices with it, like printers or iPhones. I have been looking into upgrding my iOS system but I am not sure which one I can run, if any. Right now, I am running 10.4.11, the original OS I started with. Specs are:
Model Name: iMac
Model Identifier: iMac5,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache (per processor): 4 MB
Memory: 1 GB
Bus Speed: 667 MHz
Can I upgrade to any other iOS or should I look into a new system altogether? Thanks for any guidance.