Visual Basic .Net software behaves differently from machine to machine

I've inherited a lot of custom made software for an office, and, while managing it, I've found it performs differently from machine to machine.

I mean, some controls get painted in weird ways in some machines but well in another, or just work differently, like in some machines clicking something selects it, and in the next machine clicking the same thing makes it editable.

I suspect, of course, of the myriad of DLL the software loads.

Why does it happen? Is there any way of avoiding it?

Edit:

• All the machines are Windows XP SP3, Internet Explorer 8
• "get paint in weird ways" to me means things like a control being painted 300 or 400 pixels bigger in a machine than in the others (overl开发者_如何学Goapping part of the GUI).

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I would suspect that some COM components are the issue (COMCTL32 would be my first guess), and that it isn't really a VB.NET problem. Versioning in the .NET world has been made so that the typical DLL hell issues shouldn't happen as they did before, but there are always some relics around...

Without more info I doubt that there will be a final answer to your question. You may want to start your troubleshooting by comparing Windows, Service Packs and IE versions.

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Step 1. Ensure all machines have the exact same updates applied. This goes beyond the service pack. Run Windows Update on each machine and apply everything you can. I suspect you have radically different patch levels across the board.

Step 2. Ensure all machines have the native screen resolution set. This is more important for flat panels than the ancient CRT monitors.

Step 3. Look at the video drivers. Make sure you have the latest ones for those machines.

Step 4. Make sure the exact same version of your app really is deployed across all of the machines. If there are external dependencies, verify those are the same as well.