It does not seem likely to use a document spreadsheet, such as .stw files from older OpenOffice.org, for making new spreadsheets in Microsoft Excel format (.xls, .xlsx). You need a spreadsheet template, not a document template if you want to create spreadsheet based on predefined settings.
This conversion entry was verified by us and conversion from stw to xlsx was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.