External command can't find user created *.dll on C#.NET

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From: jason (anonymous_at_discussions.microsoft.com)
Date: 06/01/04 

Date: Tue, 1 Jun 2004 12:46:08 -0700

I'm trying to run an external command-line file using user created
C:\DLL\*.dll files as following code:

Process.Start("c:\test.exe")

The test.exe has no problem when I run on the dos prompt as I set
path, C:\DLL, on system variable.

Thanks for your help