Question: Is there any way to see a list with all the active login connections on various web sites from the respective browser?

Edit: for instance if I'm logged in on superuser, stackoverflow, facebook and yahoo, is there a way to see all this in a list?

Answer: 
### Briefly

`Program Files` is where 64bit software is installed.

`Program Files (x86)` is where 32bit software is installed.

`Program Data` is where both sets of programs should write data (such as configuration data, for example) that they want to store for all users (so can't go in a single users `AppData` or `MyDocs`) and that does not belong in registry.

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The difference between the two `ProgFiles` folders allows you to have two different versions of software installed (for example Internet Explorer comes in both 32 and 64 bit flavors installed together) because Windows silently redirects requests from software in the `(x86)` folders.

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As for question 2, you can probably ignore `Program Data` most of the time (nothing should be *installed* in there), but I often find myself jumping between the two `ProgFiles` folders so I'll be looking for other answers here to help with that.
Like @DMA57361 said, on Windows Vista x64, **Program Files** is where x64 software is installed, and **Program Files (x86)** is where x86 software is installed. 

Windows (x64 versions) categorizes software this way due to a feature (for the [Windows Installer](http://en.wikipedia.org/wiki/Windows_Installer) ***Installation Cotext***) called ***“[Folder redirection](http://msdn.microsoft.com/en-us/library/dd765197(VS.85).aspx)”***. Windows (x64 versions) have this feature probably beacause that's the way they can still support and categorize x86 applications.

About the second question, the "**C:\ProgramData**" is a folder that stores user related information
that is shared by all accounts.