Yes, Oracle Services must be running (oradim has to be used), as well as account for those services must have all necessary rights - usually has.
What else makes sense to setup/check are:
oracle_sid in NT registry
NLS_LANG to american_america.... both in registry and in create database.
path to oracle_home\bin is good thing, but not very critical(?)
oracle.key in bin: THAT ONE IS CRITICAL, if exists in 7.3. Check and set its contents to correct oracle home.