I made a program using VB and I lost the source code but I have the exe file. How can I extract the code from the exe file?
Assuming your exe is a .NET assembly (you tagged the question as VB.NET), you can reverse engineer your exe using tools such as Reflector.
Since you tagged your question vb.net you might be able to retrieve quite some portions of your code using a .NET disassembler. For example try Lutz Roeder's .Net Reflector or MS ildasm which comes with the .NET compiler.
Use Reflector (assuming .NET) to dissassemble the exe back into code. You will need to create your own class structure, but you can recover the code as any of the supported CLR languages.
Have you tried Salamander, or one of the many other .net decompilers?
Trey VB Decompiler and see if that works.