I guess, technically, you have the latest G5 but that processor has been replaced a couple of times since you got the machine, so it's only the latest because it was the last.
Lay the machine flat down on its screen., put a cloth there to protect it, with the base toward you.
If you have led a good life, you will see three philips head screws on the narrow strip underneath the monitor. These are captive screws. Just release all three, hold the base and, keeping the screen flat on the table, raise the base in an arc. The whole back comes off and everything is visible.
Now, if you are like me, and did not lead a good life, you will not see any screws underneath which means that to get at anything, you will have to remove the bezel, extract the LCD screen and all will be revealed.
The only parts that you could possibly use in a PC would be the Sata Hard drive, possibly the Slot Loading DVD but that's about it. The GPU may be soldered to the board, a separate unit but not removable, like RAM can be.
The RAM is removable without destroying the machine.
If you don't plan on keeping it, why not put it up on eBay and use the money to buy a couple of PC's?
They still fetch a good price.
I have the latest iMac G5 with the iSight and slot-loading drive and all that. I have got a new one, so I no longer need the old one. (Its warranty has expired anyway.) I also have an entry-level PC. How do I open the back casing to access all the hardware? I think there's some chips inside (GPU, HDD) that I can use inside the PC. So how do I open the back cover, short of just simply breaking it apart? I see no screws, and I didn't come with any manual except a ~50 page getting started guide. Please help.
(This iMac is a 2.66 GHz system with 2 GBs of RAM, ATI 2400 card with 256 vRAM, 320 GB HDD...standard configuration for the 2.66 GHz early 2008 model.)