Windows 10 Technical Preview Build 10049 is available now. But it also has issues like the predecessor. One of the most common problems you will face is the a blue screen instead of the desktop when signing into Windows 10.
|How to fix blue screen issue and get this desktop back
To work around this issue, lock your PC (with the hardware button, or by pressing the Windows Key + L) and try signing in again.
You can also try pressing Ctrl+Shift+Esc to open the Task Manager, and then look for the lock screen (lockapp.windows.exe) listed in the processes with a “Suspended” status.
Select the process and click End Task.
Via Microsoft Windows Answer