What exactly do you mean by "opening"? VB.NET has no in-built support for the XLS file format, so you can't just open one and read it like a text file. You can read the binary data it contains, but unless you know how to interpret the format that's not much use. You can automate an instance of the Excel application, but that requires Excel to be installed. If you know your users will have Excel installed then that's OK, but otherwise it's useless. You can also use ADO.NET to access the data in the file as though it was a database. Finally, you could get a third-party component that does understand the XLS binary format. Once you've established exactly what it is that you want to do with the file and its contents, then we can advise on the best way to go about it.
