It depends on what you're doing, but more than likely, all you need is the Microsoft Access Database Engine.
This download will install a set of components that facilitate the
transfer of data between existing Microsoft Office files such as
Microsoft Office Access 2010 (*.mdb and .accdb) files and Microsoft
Office Excel 2010 (.xls, *.xlsx, and *.xlsb) files to other data
sources such as Microsoft SQL Server. Connectivity to existing text
files is also supported. ODBC and OLEDB drivers are installed for
application developers to use in developing their applications with
connectivity to Office file formats.
Edit, in response to
I just want to read and write MS excel files but i don't want to install anything on the server.
You can try EPPlus, which seems to solve your problem; though I've never tried it.
EPPlus is a .net library that reads and writes Excel 2007/2010 files using the Open Office Xml format (xlsx).