I hope you mean 600MHz machine
One way to proceed would be to download a Ubuntu or Debian 32 bit SERVER installation - (64 bit is of no use to you)
Once downloaded, check the integrity of the CD image itself. There is an option on the main installation menu for this. This could be a source of your initial problems - a bad cd burner or lousy media. Burn them as slow as you can. ( 2x 4x etc )
Once the installation succeeds ( it should ) from the console, type " sudo tasksel " and you will be presented with optional software to install, among them several graphical desktops - Gnome, LXDE, XFCE etc. I suggest you stay with a lightweight desktop - Gnome / KDE probably wouldn't run.
With this method, you have cut the potential for problems in two. If the server installation works, great. If not there is far less to troubleshoot. Let us know.