i want to transfer my oracle database to another PC. What is the easiest way to do it? Are there any GUI tools to do it?
APC's answer is the way to go for a logical transfer. If you're asking because you just want a one-time transfer to another PC then:
create the same directory structure for the database files on the second PC
copy the database files (tablespace files, control files, redo logs) to the second PC (with the database shut down on PC #1!)