Windows 10 Build 10240: Critical Error - Start menu and Cortana aren't working.

Hi Tyler,

Thank you for showing your interest in Windows 10.

I understand the inconvenience you faced. I appreciate your efforts toward solving the issue. I will certainly help you with this.

Since Windows 10 Insider Preview is still in development stage, certain features might not work in the usual manner. We are looking forward to improve it and provide the best possible customer experience in the latest coming builds. We appreciate you for sharing your valuable issue suggestion. I suggest you to provide this as suggestion/feedback on Windows Feedback app.

If you face this issue again, I suggest you to boot your system in Safe mode and check if everything works there. If it is working, I suggest you to create a new user account in Safe mode and check if you still face the issue in new user account. To create it perform the steps mentioned below.

1. Boot your PC into Safe mode by clicking on Power button on lock screen and then press and hold the SHIFT      key on your keyboard and click Restart.
2. Under      choose an option, press Troubleshoot and click Advanced options.
3. Click Startup  Settings and then click on Restart.
4. Then under Startup settings screen Press F5 to enable Safe Mode with Networking
5. Under Safe Mode, press Windows key + X key and select Control Panel.
6. Click on User accounts and Family Safety.
7. Click on User Account and then click on Manage Accounts.
8. Now click on Add a new user and follow the instructions.
9. Restart your PC and sign into new account and check      if issue is resolved.

Hope this information helps. Please feel free to reply in case you face any other issues with Windows in future.

Thank you

I'm having the same issue. Because of the critical error message in earlier builds, I created an "owner" account, which will load fine. When I sign into my personal MSN account the critical error message returns.

I was hoping when it upgraded to build 10204 this would be corrected.

When I sign out of MSN account and log in as Admin, go to "your account", click on "sign in with a Microsoft account instead" it will ask for my log in name and password, click "next" and it then asks for "the password one last time" but it will not accept the correct password. If you leave it blank, it will load, but the critical error returns.

This is very frustrating.

I finally got it fixed - hope this works for everyone else, too!

Microsoft finally released the download site for the final upgrade to Windows 10. This will work for those that had a previous build of Windows 10, as well as those wanting to upgrade from Windows 7 and 8 or 8.1

Click on the link below and you have the option of upgrading this pc or burning it to a disk. I've done both and both work fine. It will then reinstall final version of Windows 10 and save all of your programs, settings and files.

It does take quite a while to complete the process, so give yourself a couple of hours that you won't need the computer

Hope this helps - here is the link

http://www.microsoft.com/en-us/software-download/windows10?OCID=WIP_r_Win10_Body_AddPC.

This doesn't work for me. I can get as far as "Manage Accounts" but nothing happens when I click on "Add new user". It's frustrating as I was enjoying Windows 10 but feel it shouldn't have been released until this bug was fixed as I can't get into my computer unless it's on safe mode now. 

please do not call all these work-arounds, "fixes".  Thet do not fix the problem - the critical error, but are workarounds to be able to continue to use your systems. The "fix"comes when Microsoft releases an amendment to ensure this critical error never occurs on a normal, working system. At the moment, Microsoft has failed to eliminate this issue over several builds, and appears to be heading for General Release with this Critical Error bug.

Speaking as an 'old-timer', I've never delivered a General Release product with ANY known critical error bugs. But I guess it's free, so you get what you pay for.