Broken tempdb location and can't recover
Start SQL Server as an application, not a service, in minimal config mode, and only recovering master, from a command prompt:

[path to this instance]\BINN\sqlservr.exe -c -f -T3608


(Add -s InstanceName if this is a named instance.)

Now, in a different command prompt, connect using SQLCMD:

sqlcmd -S InstanceName -E


And issue a correction (triple-check this!!!), then shut the application down:

&gt; ALTER DATABASE tempdb MODIFY FILE ...
&gt; SHUTDOWN WITH NOWAIT;
&gt; GO