1. install 8.1.7 in windows.
2. create tnsentries in the tnsnames.ora of source (8.0.3)
   so that you can connect 8.1.7 in windows.
3. take a full backup of 8.0.3
4. take a full database export of 8.0. or selected schemas (login as dba )
[b]
exp username/password@source other_options
[/b]
5. Create the tablespaces and users in 8.1.7
    with the same name as in 8.0.3
6. from source ( u have to use lower version of exp and imp, so using 8.0.3 exp and imp tools)
    now import into target
[b]
imp username/password@target other_options
[/b]