Hi Daniel,
You should not be deleting the datafiles, as the datafiles will be containing the data. You can still move the datafile from one location to another(using Brtools). As you are installing an IDES system you may require more hard disk space. Please refer SAP Note: Note 1761605 - IDES ERP 6.0 incl. EHP6, which will tell you the space required for installing an IDES system. As you are installing on oracle you require atleast 250 GB for the datafiles. If you don not distribute the data while doing the installation all the data will be in the SAPDATA1.
If you have free space in some other drive move the datafile to that drive.
Thanks and Reagrds
Sheetal Joyce