Anyway, I wasn't too afraid about that, because there may exist some service which does the mapping of the folders depending on the OS language...whatever. The application seemed to be correctly installed under "C:\Programme\[application-name]\", although I specified the default path "C:\Program Files\[application-name]\"...
But the very strange things didn't even start yet. After the installed application finished to download some files, my friend wanted to open them. The application showed as location for the file "C:\Program Files\[application-name]\downloads\[filename]", and also opening it from within the application worked perfectly. As a result from that the file must exist somewhere on the hard-disk. However as soon as we wanted to go to the folder "C:\Programme\[application-name]\downloads\" (C:\Program Files doesn't exist...remember :D....I know...little confusing), the folder "downloads" didn't exist as specified by the application. At that point I really got confused, since we opened the downloaded file previously...so where should the file be stored? After some searching on the hard-disk I found out, Vista seems to copy pieces of the "Program Files" folder to "C:\Users\[your_account]\AppData\Local\VirtualStore\Program Files\"...and there was also the downloaded file.
I found this behavior strange and so after some research on the web I found this interesting link:
This behaviour is called UAC Virtualization service and was introduced by Microsoft to provide backward compatibility so that legacy systems will still work. However as you see it may result in some unexpected behavior.
What irritates me more is the strange mapping of the "Program Files" folder between the different languages. If I start the German Windows Vista explorer, there exists only the folder "Programme" which would be right for the German version.
However...when opening Run dialog (shortcut: Win-key + R) and typing there "C:\Program Files\" - which by the way should result in a "Path not found error" or similar - the explorer opens normally and suddenly the "Programme" folder is named "Program Files".