Hi Xavier,

Yes, I understand that the Windows GUI needs immediate attention. 
But I do  not agree with your argument about php scripts. I think most part of
the website is really static one. There isn't much dynamic content. Now as we
have advantage of various JavaScript libraries, I think it would leave us with
very few cases where we need to write PHP or server side scripts.
Hence, I do not believe that redesign would be very costly. 

About logos redesign, I think an update would not be immediately necessary.
The logo redesign can be pushed up when it is done.

About Windows GUI, I don't have much experience with its development, but I
think Windows Presentation Foundation (with XAML markup and C# or VB.Net etc)
would be very good choice. Can you tell me what technologies are currently
used for Windows application GUI ?