Why does Excel always open these spreadsheets?

One of my long-time Fort Wayne computer repair clients had a virus attack this year on their Microsoft Windows 7 computer. We got it cleaned up and the computer running normal again. Later, the client noticed that when they opened Excel to work on a spreadsheet three others opened. They were remnants of the virus infection. My client wanted them gone so I started the investigation. I opened Excel and then the three spreadsheets appeared. Somehow I found how they were automatically loading. A folder was found which had the three unwanted spreadsheets: C:\Users\User\roaming\Microsoft\Excel\xlstart. I deleted the three files and now Microsoft Excel starts with a blank spreadsheet just like my client wanted.