Open folders in a new window in Windows Vista or Windows XP
Since Windows 98 or so, folders you are seeing in Windows Explorer on Vista or XP will open, when you double-click on them, in the same window as the containing folder, by default. If you long for the Windows 98 approach, however, and want to open folders in a new window, there is a custom folder setting that allows you to do just that. In some older versions of Windows (including XP in some configuration), you could right-click on the folder and choose Explore to open the folder in a new Windows Explorer window - this trick unfortunately no longer works in Windows Vista.
Open folders in new Windows Explorer windows
To open folders in a new window, you will need to customize your folder settings:
In Windows XP, go to Tools > Options to open the Folder Options dialog (the same can be done in Vista with Alt+T,O). In Windows Vista, go to Organize > Folder and search Options.
The Folder Options dialog opens, with the General tab automatically selected: locate its second section of settings, labeled "Browse folders": by default, the option Open each folder in the same window is enabled; click on Open each folder in its own window, and click OK to validate your changes for Windows Explorer.
When you double-click on folders in Windows Explorer, they will open in their own window.
Under the View tab of the Folder Options dialog, you may have come across a checkbox setting labeled "Launch folder windows in a separate process" - this option, disabled by default, has little to do with opening new Windows Explorer windows for each folder. This setting, when enabled, instructs Windows to allocate memory (RAM) individually for each new Windows Explorer window. (By default, Windows allocate the same memory "pool" to all Windows Explorer windows.)