Fitnesse gives an error on Dlls loading

I have created a method in C# code.This method use com liabrary.When we try to execute from Program.Cs file this method run successfully but when i try to execute from Fitnesse it gives me an error.
<b>"System.Runtime.InteropServices.COMException (0x80040154): Retrieving the COM class factory for component with CLSID {A8A5AA2B-8D90-42DA-A2AE-26B0965AE3B2} failed due to the following error: 80040154."</b>


My code for Fitnesse tool is

!define COMMAND_PATTERN {%m -r fitnesse.fitserver.FitServer,dotnet2\fit.dll %p}
!define TEST_RUNNER {dotnet2\Runner.exe}

!path C:\Users\nitin.goel\Documents\Visual Studio 2010\Projects\HelloWorld\HelloWorldDemo\bin\Debug\HelloWorldDemo.dll

!| HelloWorldDemo.OurFirstTest |
| string1 | string2 | Concatenate? |
| Hello | World | Hello World |

!| HelloWorldDemo.OurFirstTest |
| int1 | int2 | Sum? |
| 1 | 2 | 3 |

!| HelloWorldDemo.OurFirstTest |
| Display? |
| |

!| HelloWorldDemo.OurFirstTest |
| OnApollo? |
| |