How to modify a vb app without sourcecode?

Question

I want to modify a simple vb app(.exe), but I have no source code about it. The app has a button and a textbox, when the button clicked, the textbox will be set with "7:00" and then down to "0:00".

Now, I want to do a small modification to this app: when the button clicked, don't set textbox with "7:00" but with "5:00".

Can anyone tell me how to implement it?

Answer 1

1. Fire up your favourite hex editor
2. Look for the string 7:00 in the .exe file
3. Replace it with 5:00.
4. Hope for the best.

Answer 2

Use reflector against the .exe file to get to the source code. Copy and paste into class files in new vb project. Confirm the app still functions as the original. Now make your change.

This assumes the source code hasn't been obfuscated.