Program.cs

using System;
using System.IO;
using System.Reflection;

namespace Rename
{
    class Program
    {
        static void Main( string[] args )
        {
            int begin = 46;
            int end = 145;

            var path = Path.GetDirectoryName( Assembly.GetEntryAssembly().Location );
            Console.WriteLine( path );
            var sourcePath = Path.Combine( path, "original" );

            var targetDir = "renamed";
            var targetPath = Path.Combine( path, targetDir );

            Directory.CreateDirectory( targetDir );
            for ( int i = begin; i <= end; i++ ) {
                var sourceFileName = Path.Combine( sourcePath, string.Format( "R0010{0:000}.JPG", i ) );
                var targetFileName = Path.Combine( targetPath, string.Format( "R{0:0000}.JPG", i - begin ) );

                File.Copy( sourceFileName, targetFileName );
            }
        }
    }
}