I'm sorry if this has been asked a hundred times. I'm basically thinking of trying other systems that is like Mandriva to some extent.
I would need to make sure this supports the AMD 64 bit processor (architure? possible spelling error; x86_64).

I'm not sure about these live CD's, having it run off the CD. I have a spare harddrive, so I'm really only interested in installing it on the harddrive.
Also, something somewhat complete, two or three CD's (or more) or a DVD would be nice.
If it's a smaller OS that only comes with one CD, I'll try it then.
It's just that when I started with linux, I saw mandrake was available in different number of CD's.
I'm still new to linux, so installing applications off the net or however that is done, isn't something I'm after right now, that's why I'd prefer more CD's or a DVD.

I believe that's all. I hope I explained it well enough and it's not too confusing. Sorry to have sounded pesty. I'd try looking at the distros myself, but there is a very very long list of them.

I would recommend SuSE, but the 10.1 has problems, so you should probably install 10.0 and later upgrade when more patches come out.
Also, Fedora comes into my mind, however I have had poor experiences with it so I can't recommend it, but that was a while ago (1.5 years).
Ubuntu is OK, only if you like Gnome. It has failed me (would not boot one day, and got worse with every try, so I ended up uninstalling it. That was also some time ago so it may have been fixed.)
Finally, Gentoo would be very good, but you need extensive Linux knowledge to install it.

I wanted to use GNOME using Mandriva, but it had issues when I loaded it up, so I never had the change to use it.
Currently, I'm using KDE 3.4

What sort of extensive knowledge am I looking at if I install Gentoo?

I'm not saying it's easy like mandriva. To be honest, I don't even know how gentoo is. I was told you can't just whip through installation (mandrake/mandriva) like you can windows and expect all to work.
I had no problems with that or Suse.
I did try suse 10.0 and 10.1.
I may try it again, but I was told (unless I'm wrong), that it's hard or impossible to play DVD movies.

Proselytizing is considered to be in slightly bad taste here, but since you have some Linux experience and are in the mood to experiment a bit, you might want to consider going for the gold.

Why Debian...A Sales Pitch

as long as I don't crash the PC, i'll try gentoo out. I can't say I'll be able to. I have no idea how complex the installation is, but it may be the sort of challenge I'm looking for

Gentoo: Do I install this InstallCD or the stages? Is this the introduction to the complex system?
finally, can i run gentoo when I have the x86_64?

I tried Kubunto (read it from some other forum), and I have the same issues I did with Suse.
The picture is all messed up. I can't see the desktop at all, it's just colored boxes.
As for suse, I found where to fix it, but like with kubunto, the mouse icon is gone. I can see it highlight things, and the rightlclick menu, but no cursor.