Hi,
We have been seeing a lot of instances of users having issues when upgrading from Windows 8.1 to Windows 10 whereby the system is getting stuck at 2% or is taking several hours - upwards of 12 hours - only to fail near the end of the upgrade process. This is happening on certain Dell systems with an SSD as the Boot Drive.
There have been some users who have managed to resolve this by doing a clean install of Windows 10 along with a new licence from Microsoft. We would prefer if you are seeing this issue to contact Dell Support either here on the Community Forum or on Twitter www.twitter.com/DellCaresPRO so we can investigate the issue and provide a resolution.
Further information can be found in our support article here http://www.dell.com/support/article/SLN299020
Colin