Use content of %TEMP% also in U.temp_dir instead of /tmp/ on Windows. Internal btempdir uses that anyway, so less confusing.

source/blender/blenlib/intern/path_util.c

@@ -1632,6 +1632,7 @@ void BLI_where_is_temp(char *fullname, int usertemp)
 		char *tmp = getenv("TEMP"); /* Windows */
 		if (tmp && BLI_is_dir(tmp)) {
 			strcpy(fullname, tmp);
+			strcpy(U.tempdir, fullname); /* also set user pref to show %TEMP%. /tmp/ is just plain confusing for Windows users. */
 		}
 	}
 #else