Q: I have issues with my high resolution display. What can I do?

You have to change the "compatibility settings" for JabRef to "Disable scaling for high DPI settings". Further information is available at https://www.microsoft.com/surface/en-us/support/apps-and-windows-store/app-display-issues?os=windows-10

Q: How can I use JabRef as backend for Microsoft Word?

You can directly use the references in Word's internal reference manager. Short explanation: Export your bibliography in XML format and replace the Sources.xml in %APPDATA%\Roaming\Microsoft\Bibliography. Long explanation: check out Export to Microsoft Word. Also, see https://www.youtube.com/watch?v=2PpLZTol9_o for a video explaining how to add and how to cite references in a Word document.
Another option is to use Bibtex4Word. See https://www.youtube.com/watch?v=9j3g4wfdM00 for a video explaining the usage.
The last option is to use Docear4Word, which is planned to be ported to JabRef (see JabRef4Word).

Q: How can I start or focus JabRef with hotkey ⊞+J (Win+J)?

Q: I get WARNING: Could not open/create prefs root node Software\JavaSoft\Prefs at root 0x80000002. Windows RegCreateKeyEx(...) returned error code 5.

Start regedit and create the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\JavaSoft\Prefs. [source]