Hello rgeorge.hyd,
Thanks for using the Apple Support Communities!
I understand that you Mac is not booting past the Apple logo as you would expect. I know how frustrating and concerning issues like this can be, but we are here to help! To troubleshoot this situation, there are a few different steps I would suggest.
1. Force your Mac to turn off by holding down the power button
2. Boot to OX X Recovery
3. Repair your disk using Disk Utility
After the repair, restart your Mac as normal and check to see if it boots as expected. If it does, locate the El Capitan installer in your Applications folder and attempt the install again.
Please let us know any further information if your Mac continues to have an issue installing El Capitan.
Have a great day!