"I have seen seen a used iMac G4 800 Mhz 256 ram 40 GB HD .
I am really tempted to buy it . Is it worth US $ 100 ...?
to waht Mac OS X it can be upgraded..?
what about apps ...upgrades ...etc
I cant buy any other Mac because I am out of job"
Offer the seller $80 and I'll bet he takes it.
I'm still using a PowerMac g4/1.25ghz as my "main" computer (bought new in April 2004). Still running 10.4.11 on it because I need "Classic".
It works "well enough" for most day-to-day things that I need to do. 10.4.x is no longer "current", and isn't being updated, but still works. I suppose I _could_ go to 10.5.8 if I needed to. But I have an Intel iMac for such things.
If about $100 is all you've got to spend at the moment, and you want to start using a Mac, learn about the software, etc. -- the g4 iMac will "do well enough for you" to get started on. When the time comes later on to "move up", do so. By then you'll be ready for more.
Have you seen any iMac g5's close to that in price?