Every time I boot into Windows the clock is wrong. I've tried to using freeware programs that adjust it on startup. Still wrong.

My first thought was that there is some kind of battery in my old Mac that quit a long time ago, except my Mac clock continues to synchronize with no problem.

Opening this iMac isn't something I want to try, but since I also have a stuck DVD I might have to. Ideas are welcome and much appreciated

If your signature is accurate you have an iMac5,1 and according to MacTracker, the iMac5,1 (17" 2 GHz Intel Core 2 Duo processor) has a 3 V CR2032 lithium (922-6476) Backup (a.k.a. PRAM) battery that among other things would be responsible for keeping the clock running when power is disconnected. If you have never replaced it is almost dead certain the battery has failed — a long time ago.

I found the Service Manual for the IMac5,1 and changing the battery is not a job for amateurs, or the faint of heart. It requires removing the memory access door, the front bezel, and the lower EMI shield just to get to the battery. After that removing and replacing the battery is pretty much a cinch except that you then need to replace everything you previously removed. (see page 43 of the referenced Service Manual. To get to the Optical drive requires removing a lot more stuff. I don't know what your skill level is, but I would be looking for an Apple Certified Repair Center (The iMac5,1 is obsolete so the "Genius Desk" at the Apple Store is not supposed to work on it. 😞

Thanks for finding that manual, but I have a 17" monitor, not a 20".

Disconnect your ethernet cable and turn off your wifi. This is to make sure no automatic resets are confusing our tests that follow.

Then, "zap PRAM". (hold cmd-option-P-R at startup, hold it until you hear a second chime)

Next, set your clock. Then shut down. Start up. Even if your battery is dead, the clock should still be correct. I suspect it keeps getting out of whack because pram is corrupted and it's never actually getting set. Zapping pram should fix that. If the clock is wrong, your computer may have other hardware or software problems.

Now shut down. Unplug power. Wait 30 seconds. Plug back in power and turn back on. Check clock. If it's reset to something old, your battery needs to be replaced. Otherwise you should be fine.

Reconnect your network. You might also want to make sure your clock prefs are set to keep the clock up to date automatically. (though this is actually not incredibly reliable...)