iMac Completely Froze - Won't boot from Install Disc! Help!

Somewhere in 2009/2010, I can't really remember now I bought the 21inch iMac. It was working perfectly fine up until January 2011 where it started lagging, it became very slow and eventually it kept freezing...

It is now completely unworkable, it originally has the Mac OSX Leopard system and I cannot at all use it. When it is powered on it stays on the apple screen for like 10+/- minutes. After a while the background shows up but nothing on screen and it sits there frozen. When the power button is pressed once, the screen turns off, when the power button is pressed again, screen comes back on with everything already loaded, you can see the dock, and startup programs but everything is completely frozen, I can move the mouse but apart from that it's all dead (even the keyboard). After like 10/20 +- minutes it unfreezes and the computer is usable... the problem is that it keeps freezing every now and then...

While it unfroze, I managed to use a tool called Yasu to clean it up, I also checked the hard drive (1TB one) and everything was said to be in normal conditon.

Rebooted the mac, and the same thing happens all over again...

I tried running the install disc that originally came with the iMac but it does not want to boot. I tried booting in safe mode, it takes ages to boot up and when it does, it freezes on the login screen. I used the applications CD where you have to hold D, this booted up, I checked the system and everything was completely fine.

I then tried booting up (holding C) from a Windows Live CD, and it booted up perfectly fine, did a disk check, all was stated as working.

I then tried booting from the install disc and it just won't boot. It freezes up and I have to wait like 10 to 20 minutes to take out the CD because it won't come out.

Before I take it to Apple (#!££$"£# piece of ****) I would like to see if there's anything else I can do?

Since other CD's are booting up perfectly fine, I was thinking of installing Ubuntu Linux and maybe then trying to reinstall Mac OSX using the original CD?

Any help? Please!!!!!!!!!!!! and thank you in advance.

Im no expert but it sounds like you might have a bad install DVD.

Do u know someone who has an 10.6 install disk you could try? if not, As the Mac is still new (ish) i would just take it into a Apple store, even if its just out of warranty they will likely fix it for free.