Wubi with 14.10 doesn't work - failed to partition the selected disk

Solution 1:

This is a bug with the wubi.exe released with 14.10. Or to be precise it's a bug in one of the programs used byubiquity (the Ubuntu installer). Normally bugs can be fixed, but typically Wubi is never patched mid-release so this bug will remain for the full life-cycle of Ubuntu 14.10.

So, if you have tried to install Ubuntu with Wubi 14.10, it doesn't work and cannot be fixed with any known manual workaround.

Go to the Add/Remove programs in the Control Panel in Windows, and double click on the Ubuntu entry to completely uninstall Wubi.

Update

There is now a manual workaround from hakuna_matata that is of medium to high difficulty. You have to apply it in Windows, prior to the Ubuntu install phase. See ubuntuforums for more information.