For example, let's say that currently your system looks like this

Oracle is installed in
c:\oracle

You have 3 tablespaces/datafiles in your database (other than system, rbs, etc)
d:\oradata\users01.dbf
d:\oradata\index01.dbf
e:\oradata\tools01.dbf

When you export (read the docs), you will get a file, you can call it anything, say export.dmp. Then you can reformat (after transfering the dump file somewhere else of course)

After you create the new database (follow the proper steps), you will run import (read the docs) on 8.1.6 with the export.dmp you transfered back to that machine. The new database you have will have it's own control files, etc. The only thing you need from the previous database is the full export file.

If you don't pre-create the tablespaces, import will try to import them to their original location (d:\oradata and e:\oradata). If those don't exist you might have to create them, or it will yell at you first saying they're not there, I'm not sure as I always do it the right way :)

You could also pre-create empty tablespaces/datafiles and import will use those instead.