Bytescout XLS Viewer - a free (for personal usage) freeware program which allows you to view XLS, XLSX, CSV & ODS documents without using Microsoft Office. The interface isn't particularly elegant, but since there's no other software to convert the documents to Word or Excel, the functionality is adequate. You can open a variety of documents with this program, including spreadsheets, Word documents, Power Point presentations and others. This is a great little freeware for anyone who needs to view the documents as simply as they would in their favorite word processor. You can save the information directly to a PDF file with one click.
ByteScout XLS Viewer - a free program which allows you to view your chosen format of XLS file. This is a great little tool for Excel users who need to view xls file from within Excel. It displays the same format as the original document, allowing you to do almost all Excel functions from within the viewer.
It was developed by a few veteran computer programmers. The team managed to produce an excellent product. If you are an Excel user, XLS Viewer should be in your download list. It can open most common types of XLS files, including Word, Excel and PowerPoint. If you're unfamiliar with Word, this tool is very useful as it allows you to view PDF and ods format documents directly in Excel.