When Build 9879 released for Windows 10 Technical Preview a number of beta testers had problems installing a specific update. The update, KB3020114 was meant to eradicate the reported Explorer.exe crashes that a multitude of Windows Insiders experienced right after Build release.
For some, the update installed just fine, but most others were left with a version of Windows 10 that was unusable. Microsoft provided a workaround which involved running a command in a Windows 10 CMD windows and then rerunning Windows Update, but the company kept working to finalize a proper resolution.
Gabe Aul, the Windows Insider lead at Microsoft, reported on Twitter that a HotFix is now available through Windows Update.