Am using Excel 2007 version.

I had posted an excel file (with 10 questions with 4 options for each
question, drop down option is used) to about 100 customers to fill the
answers and post it back to me.

So, now i have 100 excel files. I need to combine all those into one excel
sheet so that it will be easy to analyze, segregate and for further
processing.

So how to combine the data available in these excel sheets.

Please explain the solution 'clearly' such that a layman can understand.

Thanks in advance