- unload the data to a csv-file and then use sqlloader to load into Oracle
- use MS Acces with two linked tables, one for the SQLServer side, one for the Oracle side
The first options to me seems the best one.
PS Why do you want to load it into Oracle 7.3. That version has been obsolete for several years. I suggest you at least should go to 8i or even consider 9i. 9i even has options to access a datafile as a table!