How can I start Surface pro 3 when is blocked by blue screen because of bit-locker problem

Hello Dr. Michael Kollmannsberger,

Welcome to Microsoft Q&A.

Could you please make it clear to us what is finally displayed on the screen of your Surface Pro 3 at this moment?

Is it a BSOD page:

Or a page asking you to enter the Bitlocker recovery key:

Based on your description of the problem, I am more inclined to judge that after pressing the power button on your Surface Pro 3, you can only see the BSOD page, but it cannot start up and enter the system normally right? Then I'm afraid there is no other way to enter the Bitlocker recovery key page now, unless the BSOD can be resolved first.

Please refer to the information in the following support connection to create a dedicated USB recovery drive for your Surface on another computer. Then try using it to fix your Surface:

Creating and using a USB recovery drive for Surface - Microsoft Support

There is a video step in the link. But please pay attention at 2:11 of the video. Please click Advanced options instead of Recover from a drive. At this time, you will see various troubleshooting options. It is recommended that you try Startup Repair:

Since your device is encrypted, you may see the page asking you to enter the Bitlocker recovery key again at this time. Try entering the Bitlocker recovery key and proceed to the next step.

If you can re-enter the system in this way, then at least you have all the conditions for backing up the data. However, if you still can't access the troubleshooting page with the dedicated USB recovery drive for Surface, then there is only one last method left: follow the video process to restore your Surface to factory Settings.

Best Regards,

Ami | Microsoft Q&A Support Specialist