xls to csv

Hi all folks,

I hope I can get some help here about a prob I'm having...I need to export an xls file to a csv format. It is apparently as easy as choosing the "Save as" correct format, but I can't get it...

I think it's clearer to see if you have a look to the attached files...The final result I want to obtain is as in the attached file "Dispositivos de protección.csv" (a csv file with columns separated by commas) and the source xls file for converting to that csv format is as in "Articulo_y_descripccion.xls"

I think the person who sent me the file "Dispositivos de protección.csv" got to convert it through an excel wizard (Text import wizard), but I'm not even sure of this because that wizard is rather for importing, not for exporting.

Anyway, whenever I try to save "Articulo_y_descripccion.xls" as a csv format file, I got a popup message warning about a possible problem of compatibility and giving the option to save it with other name...I don't truly understand why is this...

I can't manage to make this file conversion with the excel but instead I have found an app called convert XLS which makes it perfectly ( I've tried other ones and didn't get the wished result)...Unfortunately this app is too expensive to me...

I wonder if there are other ways to make this conversion...
Hope you can help me,
Thanks in advance,
Buhnen