To stop the file conversion process, I had to cancel the install (along with the file conversion) and re-install. I was crossing my fingers in the hopes that nothing would be lost from my disk. Nothing was. I can't make ANY guarantees to you that you won't loose anything!!!
The El Capitan installer is named “Install OS X El Capitan”. This program is removed after install finishes. If it is gone, you will have to download it again. The recovery partition tools will let you connect to the app store and download another copy. You will find "/Applications/Install OS X El Capitan" if it has not been removed.
Obtain an 8 or 16 GB thumb drive.
Boot into the recovery partition by holding down the option key while rebooting.
Once the system is up, start the utilities residing there and look for /Applications/Install OS X El Capitan. Download if missing.
Insert thumb drive.
Format the thumb drive using the Disk Utility to format it to HFS+ with a GUID partition scheme, naming it INSTALLER.
Turn the thumb drive into a boot device installer using a Terminal session (double-click on /Applications/Utilities/Terminal. Hit "command +" a few times to enlarge terminal text if needed). note: Anytime you type something with spaces in it, each space MUST be prefixed with a backslash. Thus the funny looking command line below interspersed with backslashes. Copy+paste the following command line into the terminal:
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/INSTALLER --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
It will ask for your password. Enter it, hit return and soon you will have a new, bootable install device.
Boot off of the thumb drive (reboot with option key held down) and soon you will see the El Capitan install process unfolding on your terminal. I did not re-request encryption of my disk. When the install is complete, remove the thumb drive and reboot. Good Luck!
I saved a copy of the install file so that I would not have to wait through another download if something went wrong.
A good resource