NUNIT on X86 build throws System.BadImageFormatException on dll load

hi i am trying to use nunit-x86.exe to load a C.dll. This C Dll is same as my Net.Dll which calls the same interfaces (via another unmanaged Dlls). I have no problem running the .Net version of the DLL using nunit-x86.exe, but i cannot load the C version it in nunit

I changed the project configurations from win32 to x86. This changes the dot net dll project to x86, but the C dll has only the win32 option. The C dll which contains the test fixtures etc compiles and links fine

Below is the exception from nunit

 System.BadImageFormatException: is not a valid win32 application. (Exception from HRESULT: 0x800700C1

    System.BadImageFormatException...

Server stack trace: 
   at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
   at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
   at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.Load(String assemblyString)
   at NUnit.Core.Builders.TestAssemblyBuilder.Load(String path)
   at NUnit.Core.Builders.TestAssemblyBuilder.Build(String assemblyName, Boolean autoSuites)
   at NUnit.Core.Builders.TestAssemblyBuilder.Build(String assemblyName, String testName, Boolean autoSuites)
   at NUnit.Core.TestSuiteBuilder.BuildSingleAssembly(TestPackage package)
   at NUnit.Core.TestSuiteBuilder.Build(TestPackage package)
   at NUnit.Core.SimpleTestRunner.Load(TestPackage package)
   at NUnit.Core.ProxyTestRunner.Load(TestPackage package)
   at NUnit.Core.ProxyTestRunner.Load(TestPackage package)
   at NUnit.Core.RemoteTestRunner.Load(TestPackage package)
   at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs)
   at System.Runtime.Remoting.Messaging.StackBuilderSink.PrivateProcessMessage(RuntimeMethodHandle md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs)
   at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg, Int32 methodPtr, Boolean fExecuteInContext)

Exception rethrown at [0]: 
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at NUnit.Core.TestRunner.Load(TestPackage package)
   at NUnit.Util.TestDomain.Load(TestPackage package)
   at NUnit.Util.TestLoader.LoadTest(String testName)