Show file extensions in SharePoint Doc Lib

1. Open up the .aspx file responsible for displaying the document list in Sharepoint Designer, (eg. AllItems.aspx)
2. Select the WebPartPages:ListViewWebPart control. (It is the place where rows of document are listed)
3. Right-click on it, Convert to XSLT Data View
4. Go into the code and find the line that says:
<xsl:value-of select="ddwrt:UrlBaseName(string(@LinkFilename))" />
5. Add this to the end of the line:
.<xsl:value-of select="@File_x0020_Type" />
6. Save   

Caution is - After editing the file with sharepoint designer, file might not edit with anything, except maybe Visual Studio