You have installed Inventor 2015 and you noticed that Thread Features are off by default in a drawing view.
We made a change in the 2015 Release so Inventor remembers the drawing view settings you used and will reuse them next time you place a view. This change was meant to keep the user choices and save clicks on view creation.
Thread Features in part view are off by default in 2015, but once you enable them in a part view, Thread features option will persist until you place a part view where you uncheck it.
The last used settings are stored in three 32 Bit Registry Key. One is for Part Views, the other for Assembly, and the third one for Presentation views.
The RegKeys are named BaseViewDefAssy, BaseViewDefPart and BaseViewDefPres. They are located in
HKCU\Software\Autodesk\Inventor\RegistryVersion19.0\Applets\DrawingLayout\
\Preferences\\DrawingFormat.

If you want to dig a bit deeper and understand the RegKey value, each bit stores last used status of the following Base view dialog controls:
- Thread feature
- Interference edges
- Tangent edges
- Foreshortened
- Hidden line removed
- Shaded
- Free-NotUsed and set to 0
- Free-NotUsed and set to 0
In the registry setting the first 8bits (Bit 0 to 7) belongs to Front - Current - Ortho projected view type. Next 8bits ((Bit 8 to 15) are used for Iso Projected views, next 8bits are not used, final 8bits are used for Flat Pattern views.
You can use a calculator with a programmer mode so you can easily check which bit is enabled or not.
For example : If Bit 0 is set to 0 and Bit 8 is set to 1, it means thread features will be enabled in Iso Projected Views, but not in Front - Current - Ortho Views.
If Bit 5 is set to 0 and Bit 13 is set to 1, Shaded Views will enabled in Iso Views but not in in Front - Current - Ortho Views.

Pierre Masson