To convert all files at once, in the current release of the software choose File > AutoPilot > Document Converter.
However, if you just open a 5.2 file in the current release of the software it will be converted without problems.
5.2 files can be read in the current release, but not vice versa. However, you can save any current file to 5.2 format by just choosing File > Save As in the current release of the software.
If you want the default file format to be 5.2 when you're using the current release, choose Tools > Options > Load/Save > General, and set the default file formats to 5.2 in the Standard File Format area.
When converting StarOffice 5.x files to the current release either manually or using the AutoPilot, all StarOffice software objects embedded as an OLE object, such as charts or graphics, are automatically converted to the new release's XML format.