Converting .xlsx files to .sav format.
Converting Microsoft Excel Spreadsheets directly to SPSS Data Files (.xlsx to .sav conversion) should be possible when using GNU PSPP, an open source statistical software. To do so, you might, however, need to first convert .xlsx to .csv.
There are numerous web-based conversion utilities capable of converting .xlsx to .sav, such as the coN'verter (by n'counter).
A simple web-based SPSS to Excel Converter
A free alternative to SPSS