Q: After downloading & installingOS X El Capitan, my Mac Book Pro will not open , nor respond to my password, Instead a blue screen appeared.  Hari

Resolve startup issues and perform disk maintenance with Disk Utility and fsck

The X Lab: Troubleshooting Startup and Login Items

Top 10 Troubleshooting Tips for Mac Startup Problems

- Try resetting the SMC and NVRAM/PRAM

Intel-based Macs: Resetting the System Management Controller (SMC)

About NVRAM and PRAM

- Try starting in Safe Mode

OS X: What is Safe Boot, Safe Mode?

- Boot to Recovery and repair the startup disk

OS X: About OS X Recovery - Apple Support

- If it is repairable reinstall the OSX

How to reinstall OS X on your Mac - Apple Support

- If you do not have a backup use disk utility to restore the internal disk to an external disk so you can try to recover data.

Then format the startup disk and do a fresh install of OSX

BTW, this is the Mac Pro desktop forum

Please read this whole message before doing anything.

This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.

I am currently having a similar problem. After updating El Capitan to the latest version, two days ago while web browsing I received my first blue screen. After hard shutting down my computer and turning it back on I entered my password and the profile only loaded halfway before the screen quickly flashed black and then turned white. My fans proceeded to turn on full power and it just sat there doing nothing. The only way I could actually boot my profile back up was to boot in safe mode go to disk utility and do first aid on the drive. This allowed me to log back in normally only for a short period of time before it happened again. After all of this I thought maybe it was my hard drive going bad or something so I wiped it and did a clean install. This did not fix anything. Next I decided run diagnostics using Command D on bootup. Nothing was appearing to be bad after a 2 hour long test. I really hope they get a fix out soon because this is hindering my ability to do schoolwork which is online.. I have currently tried everything that lllaasshas mentioned and nothing has helped this issue.

Edit:

Another problem I forgot to mention was that if it is working correctly, if I shut my laptop and reopen it, the screen remains black but the key lights goes on and off when I tap the power button. This forces me to hard shut down and I have to repeat the steps of safe mode boot up in order to log back in.