You can edit with OpenOffice.
Start, OpenOffice.org, open a document, (do your editing)...
Click File,Save as, Select Microsoft PowerPoint, click save.
Saving as a Microsoft Office File
1.Choose File - Save As.
2.In the File type box, select a Microsoft Office file format.
Saving Documents by Default in Microsoft Office Formats
1.Choose Tools - Options - Load/Save - General.
2.In the Standard file format area, first select a document type, then select the file type for saving.
From now on, if you save a document, the File type will be set according to your choice. Of course, you still can select another file type in the file save dialog.
