If you have not yet attempted a Ubuntu install, suggest you also take a look at Linux Mint, also free, ( see
http://linuxmint.com ) which is based on Ubuntu, as it has a more User friendly Desktop interface. For user comparison feed-back on Ubuntu v Mint see:
http://www.itworld.com/article/2915531/linux/is-linux-mint-better-than-ubuntu.html
Regarding your Critical Error issues with Windows 10, it may be worth trying a Windows 10 Reset operation that will most likely fix your critical error problems. Best to do this before attempting to install a Dual Boot Linux system alongside Windows 10.
To carry out a Win 10 reset you start Windows 10 and log on as usual and proceed as follows:
* If you have an Anti-Virus program such as AVAST installed, recommended that you remove it before attempting a Win 10 reset. To remove it continue:-
- Press the Windows Logo Keyboard Key and "X" key combination together
- Select 'Control Panel'
- Select 'Uninstall a Program'
- Scroll through the list of installed programs and Select/Highlight 'AVAST
- Click 'Uninstall' to remove AVAST
* To perform a Windows 10 Reset continue:-
- Press the Windows Logo Keyboard key and "I" key combination together to access the Windows Settings panel
- Select 'Update & Security'
- Select 'Recovery'
- Below the text 'Reset this PC' select 'Get Started'
- Choose the Option 'Keep my files'
- Follow the on-screen instructions to perform a Windows 10 reset operation
If Windows 10 is now working ok, Time to install Linux Mint (or Ubuntu):-
- For Mint dual boot with Windows see
https://sites.google.com/site/easylinuxtipsproject/mint-install
- For Ubuntu and other Linux distributions dual boot see
http://www.pcworld.com/article/2955460/operating-systems/dual-booting-linux-with-windows-what-you-need-to-know.html