Switch the default system temporary tablespace

create temporary tablespace temp_new tempfile
'd:\oracle\oradata\test\temp1.dbf' size 500m autoextend on next 10m maxsize unlimited
extent management local;

Switch to new temporary tablespace. You may need to switch the temporary tablespace to new one to reduce the size of the current tempfile and remove it.

alter database default temporary tablespace temp_new;

You may not switch until the tablespace is in use.

Drop the old one .

drop tablespace temp_od including contents and datafiles;