]Have you done what Melodie asked about the md5sum check (and could check if the cd burn is okay)
psioniks, you can use either or these tools to check the integrity of your iso, they both work under Windows:
http://www.md5summer.org/http://wxchecksums.sourceforge.net/mainpage_en.html512MB ram isn't a great deal, but, as important, do you happen to know what graphics card you are using and how much ram it has - or if it's sharing your main 512 ram? (which would mean even less main ram for the OS to use)
If it turns out it's a limitation on your hardware specs you may want to consider the PCLinuxOS versions of lxde or Openbox or xfce Phoenix as they run better on lower spec machines.
+1. The choice is : Xfce4, much lighter than KDE, has also many gui configuration tools, Lxde, is the lightest providing a Desktop Manager, which is quite good for daily use, Openbox, which is the Window manager used in Lxde, and is provided with a few light tools creating the desktop environment, therefore the lightest actually supported officially, but needs to learn a bit more when it comes to customize it.
My humble opinion : 512 MB ram I think will be best with a Lxde version, particularly as you are a beginner under Linux.
