Opening XLT in Google Drive
XLT is the file format used for Excel templates. Sometimes you will end downloading these templates for Excel files in order you can edit them and save as a spreadsheet in any desired format. If you use Excel then the format will be likely .xlsx or .xls
Unfortunately Google Docs (Google Drive) only let you preview the XLT files, but if you need to open it and edit the spreadsheet (use the template) then a good option if you don’t have Excel installed in your computer is to convert the XLT to XLS or XLSX using online tool.
If you have Excel installed, then you just need to open the file and then save it as a XLS or XLSX file and you can upload that file to Google Drive and then it will be converted to the Google Drive format.
A few services that let you convert the XLS files online are Zamzar and YouconvertIt.