Why can't my application find a dependent dll in the same directory?

I have a simple console test application, `ConsoleApplication1.exe`, which references another assembly `clipper.dll`. On 3 machines that I've tested it on, it is possible to place both files in e.g. `c:\test\`, and execute `ConsoleApplication1.exe`. On one other machine, which happens to be a client machine, running `ConsoleApplication1.exe` results in a program crash and the following being printed to the console: ``` C:\test>dir Volume in drive C has no label. Volume Serial Number is 7C46-414F Directory of C:\test 07/12/2010 06:08 PM <DIR> . 07/12/2010 06:08 PM <DIR> .. 07/12/2010 05:13 PM 11,776 ClassLibrary1.dll 07/12/2010 05:13 PM 30,208 ClassLibrary1.pdb 07/12/2010 04:55 PM 3,572 ClassLibrary1.tlb 19/11/2010 02:46 PM 235,008 clipper.dll 19/11/2010 02:46 PM 1,534,976 clipper.pdb 07/12/2010 05:13 PM 6,144 ConsoleApplication1.exe 07/12/2010 05:13 PM 11,776 ConsoleApplication1.pdb 01/08/2010 12:52 PM 139,264 nunit.core.dll 01/08/2010 06:41 AM 57,344 nunit.core.interfaces.dll 01/08/2010 06:41 AM 135,168 nunit.framework.dll 01/08/2010 06:41 AM 547,262 nunit.framework.xml 11 File(s) 2,712,498 bytes 2 Dir(s) 477,821,784,064 bytes free C:\test>ConsoleApplication1.exe Unhandled Exception: System.IO.FileNotFoundException: Could not load file or ass embly 'clipper.dll' or one of its dependencies. The specified module could not b e found. at ConsoleApplication1.Program.Main(String[] args) ``` This is a odd to me, although I don't understand dll load rules comprehensively I thought it would search the CWD for the specified file. And the fact this same setup works on the various other computers I've tried is also odd. Curiously, on a working computer if I remove clipper.dll and then run it: ``` C:\Temp>ConsoleApplication1.exe Unhandled Exception: System.IO.FileNotFoundException: Could not load file or ass embly 'clipper, Version=1.0.3975.26584, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified. at ConsoleApplication1.Program.Main(String[] args) ``` The unhandled exception is slightly different, with a full assembly name. - Both `ConsoleApplication1.exe` and `clipper.dll` are built for .NET 4. - All machines have the .NET 4 runtime installed. The problem machine does not have the .NET sdk - clipper.dll is a combination of ummanaged c++ code and C++/CLI. It is a suspicious character because it is basically the first C++/CLI .NET assembly I have created and much fumbling was involved. It seems to load in reflector fine. - These efforts came about when I was trying to figure out why I was unable to successfully utilise a COM object (call it `foo.dll`) which also referenced `clipper.dll` - all also on the same problem machine. After several hours of regasm hell I was able to further isolate it to this.