Solution: Freezing At Boot Up After Upgrading BIOS in LENOVO IdeaPad Z50-70

Lenovo has identified root cause for an issue that causes Lenovo ThinkPad systems with Broadwell and Haswell chips to hang or freeze at OS boot after upgrading the BIOS to versions released in August 2016. This is known to occur on ThinkPad systems running Windows 7 and Windows 10 installed via legacy Windows 7.

Root cause was identified as a conflict between the BIOS and a feature in ThinkPad Power Manager for Dynamic Brightness Control. This setting is disabled by default, so only customers who enabled the feature would encounter this issue.

Try this:  Change the BIOS Setup to disable Execution Prevention setting:
Power on the system and press F1 key to enter the BIOS Setup.
Move to the Security page and goes to the Memory Protection subpage.
Change Execution Prevention to Disabled.
Press F10 to save and exit the BIOS Setup. Then, boot to the operating system.

Disable the Dynamic Brightness Control for the Shutdown/Start up feature of ThinkPad Power Manager:
Boot to Windows 7 and open ThinkPad Power Manager. If the system is running other than Windows 7, ignore all the steps described below.
Switch to the Advanced menu and go to Global Power Settings tab.
Show the Dynamic Brightness Control settings. All settings are disabled in default.
Uncheck “Shutdown/Start up” items. Other settings can remain as-is. 
Save the settings and close Power Manager.
Reboot the system and go to BIOS Setup again. Then, set the Execution Prevention setting back to Enabled.
Press F10 to save and exit the BIOS Setup. Then, boot to the operating system.

Source from support.lenovo.com

LENOVO IdeaPad Z50-70 battery

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Capacity: 2800mAh (41Wh)
Battery cells: 4-cell
Chemical: Li-ion
Battery Color: white
Condition: new original battery
Warranty: 9 months

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