I hope you don't already have sites and/or users setup on it, as that was specifically warned against in the ISPConfig documentation, but no matter what, you will have to at the very least, delete your installation folder, delete the /root/ispconfig/* tree, and delete/drop any mysql database created by this installation.
If the installation had completed normally, there would be an uninstall script in /root/ispconfig, but you may not have gotten that far before it bombed out. If not, you have to manually do the 3 things mentioned first. After that, you can go back through your instruction set and copy/paste all of the commands to install and configure software for the server setup, just to be sure, since the worst that can happen is that apt-get install [whatever] will give you and error message that package xyz is already installed, and at best, will install something that you didn't successfully get installed the previous time.
Hopefully you only have a missing package issue, not a configuration problem, since not knowing what you have or where it is kept will keep you from being able to go back to original (clean install) configuration and at my level of inexperience, the only way I know how to reset the configuration files is to wipe and reload.
If you do get your packages all installed, try to ftp in and upload the ISPConfig install file, which will verify that your ftp server is working too. Copy or move it to /var/tmp, re-extract, and re-install. Keep an eye on the PuTTY window for errors (You *are* doing this from a remote shell, right?), and keep in mind that if it installs correctly, this process will end up taking MUCH longer than before when it erred out and stopped prematurely. YMMV depending on the speed of your server, but I found that it took almost a hour to completely run through the installation script when it was working correctly vs. something like less than 6 minutes when it gave me your original errors.
Remember that copy and paste are your best friends, and you might even consider pasting onto a very boring plain text editor that you can change fonts on, just in case you have some visual confusion over what some character is in your web browser font vs, what the actual ascii character really is. If you have any doubts over whether something is a one or the lower-case letter "L", change the font and look at it again for a 2nd opinion, if it may make a difference.