Firstly at all, download ubuntu server 9.10 and burn the iso file
http://www.ubuntu.com/getubuntu/download
http://www.ubuntu.com/getubuntu/downloadmirrors
http://kambing.ui.ac.id/iso/ubuntu/releases/
ftp://kambing.ui.ac.id/iso/ubuntu/releases/
ftp://dl2.foss-id.web.id/iso/ubuntu/releases/
http://mirror.unej.ac.id/pub/iso/ubuntu/
ftp://mirror.unej.ac.id/pub/iso/ubuntu/
http://repo.ugm.ac.id/iso/ubuntukarmic/
ftp://repo.ugm.ac.id/iso/ubuntu/karmic/

secondly, prepare the desktop PC which dedicated as proxy server. Herewith share my proxy PC specification during testing and installation:
Mainboard: Gigabity GA-945GCM-S2L/S2C
Processor: intel 2 core 2.0 GHz
RAM: Kingston 2GB (2 slots used)
LAN: onboard

First, let’s start the installation for ubuntu server:

1. Do not plug the LAN cable
2. Install ubuntu server 9.10 at the PC which dedicated as proxy server.  Following step by step ubuntu 9.10 karmic lamp server installation guide until the step of detecting network hardware in progress.
3. It’s fail for DHCP configuration and will then asked for manual network configuration. In this step, you can configure the proxy IP as you needs depends of your network routing configuration.
4. Once finished IP proxy configuration, continue for the rest and follow the next step which shared at step by step ubuntu 9.10 karmic lamp server installation guide until finished.
5. Now, ubuntu server 9.10 been successfully installed then try to ping to the main server (router) and www.google.com
6. Successful pinging? It’s means that the proxy server had been communicating with your local network and internet. If fail, just binding the mac address of proxy server and reboot both main server (router) and proxy to refresh the connection.

Well done, ubuntu server successfully installed, now continue for webmin and proxy-squid installation through APT repository:

1. login ubuntu server by type username and password
2. login as root, type the command sudo su
3. login as root by typing the username and password
4. insert the source list by command vi /etc/apt/sources.list
5. Press i on the keyboard and go to last line. insert new line deb http://download.webmin.com/download/repository sarge contrib
6. press esc on the keyboard then continue pressing wq! to exit from sources list
   
7. Get webmin jcameron by run the command wget http://www.webmin.com/jcameron-key.asc
8. Then run the command sudo apt-key add jcameron-key.asc
9. continue to run the command sudo apt-get update
10. Please wait and ensure all update being completed and back to the prompt
11. Finished, then continue to install the webmin by typing the command sudo apt-get install webmin
12. Webmin installed, the server will booting then shown to you the address to view or remote the webmin through the browser https://your-ip-address:10000/ (ip-address as defined during ubuntu server installation)
13. Finally, installed the proxy-squid by command sudo apt-install squid

Everything done, the webmin with proxy-squid installed and now continue to access the webmin through browser https://your-ip-adderss:10000/

Finished and you can see the proxy squid under servers directory