I have problems encoding files in Visual Studio 2008. When compiling, I get errors like this:

When I try to open a file where a specific error occurs, an encoding window appears:

Defined by auto-detect defualt. When I change the encoding to UTF-8, everything works. If I open every problem file in my project using UTF-8 encoding, the project starts compiling. The problem is that I have too many files, and it’s funny to open each file and set the encoding to UTF-8. Is there any way to do this fast?
My VS settings:

I am using Windows Server 2008 R2.
UPDATE:
For Hans Passan and Noah Richards. Thanks for the interaction. I recently changed my operating system, so everything is fresh. I also downloaded the new solution from the control source.
In the regional OS settings, I changed the system language to Polish (Poland):

In VS, I changed the international settings in the same way as the windows:

The problem is still not resolved.
When I open some .cs files using automatic detection for encoding and then check Files → Advanced save options ... some of these .cs files have code page 1250:

but internally looks like this:

It is connected because when I check the properties of such specific files in the source control, they seem to be UTF-8 encoded:

I do not understand this discrepancy.
All other files are UTF-8 encoded:

and opens correctly. I have no idea what is happening, because, as far as I know, my friend has the same parameters as me, and the same project compiles it correctly. But so far, he has not happily encountered coding problems.
visual-studio-2008 visual-studio
jwaliszko
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