Windows programs will not run natively on Ubuntu. You would probably be able to run them in Wine (a Windows compatibility layer for Unix-systems), but in most cases, there is also a Linux version. If you're looking for alternative programs simply browsing the software center (search for "Ubuntu Software" in the dash) will get you results, if not, search the web or check out alternativeto.net. They have a filter option for Linux programs.
Be careful fooling around with folders outside your home directory. Usually you're supposed to install apps using the
apt-get install application-name or
snap install application-name command, from the software center, or by downloading and installing .deb files.
But if you need to do something funky in
etc, just prefix your commands with
sudo or type the sudo bang bang (
sudo !!) command directly after you issued a command with insufficient permissions. If don't want to retype the sudo command every time, you can issue
sudo -i to login as root or
sudo su to log in as root and stay in your home folder. Doing this will give you administrative rights within that terminal session. After you're finished, type
exit to log back in with your user account or close the terminal window. But be careful: With great power comes great responsibility. And don't drink and
Also, most programs don't go in the
etc folder. Use
opt. If you're using wine to run your old windows apps, you will use what is called a virtual C drive - essentially just a folder inside you home directory. Detailed instructions can be found on their website.