自Vista及Win7開始，微軟更改了原有的應用程序存儲目錄結構，（XP是Application Data）系統盤：用戶\用戶名\Appdata, 並分為Roaming, Local,及 LocalLow三個文件夾.
更改原因如下:
• 優化登錄速度
• 根據使用安全級別分別訪問不同文件夾
Windows 使用 Local及LocalLow文件夾存放非漫游的應用程序數據（類似注冊表Local_machine）及一些空間占用大無法漫游的應用程序數據，而Roaming文件夾則用來保存可漫游的用戶應用程序數據，如每個用戶的個性化設置等。
The Roaming folder is to preserve user data. Imagine a company with 1000 workstations, and employee use different workstations each day. By roaming the user profile data (copy to server), the custom data is always available regardless of any workstation the employee uses.
The applications choose whether to save to local or roaming, and roaming is used by default by most applications, it acts as local to people not on a domain, and to people that are, their settings follow them.
Local is only typically used when explicitly preventing settings following a user across a domain. This will be usually due to size of the settings folder to prevent having to transfer gigabytes across a domain in cases such as cache. For example Chromium (web browser) uses local instead of roaming as it’s cache folder is within the user settings folder. Most other applications separate the cache and settings for this reason.
The naming of local and roaming is unfortunate, as most users at home aren’t on a domain and can easily be confused by such terms.
Roaming is the folder that would be synchronized with a server if you logged into a domain with a roaming profile (enabling you to log into any computer in a domain and access your favorites, documents, etc. Firefox stores its information here, so you could even have the same bookmarks between computers with a roaming profile. It is worth to remember that “Roaming” folder is synchronized with the server meaning bigger the size of roaming folder longer the time required to logon to a PC. The folder “Roaming” by design ensures that ONLY absolutely essential data like “Favorites” “Desktop” and “Documents” travel with the user thereby making it as a roaming profile.
Local is the folder that is specific to that computer – any information here would not be synchronized with a server. This folder is equivalent in XP to C:Documents and SettingsUserLocal SettingsApplication Data.
LocalLow is the same folder as local, but has a lower integrity level. IE8, for example, can only write to the locallow folder (when protected mode is on).
1、Local和Roaming之間的區別：Local 比較大，非漫游應用數據。Roaming 一般是漫游應用數據。
2、Roaming和locallow之間的區別：
roaming文件夾是Windows存放一些使用程序后產生的數據文件，如空間聽音樂，登入的號碼等而緩存的一些數據。
Appdata下有三個子文件夾local，locallow和roaming。
1、當解壓縮包時如果不指定路徑，系統就把壓縮包解到local\temp文件夾下，存放了一些解壓文件，安裝軟件時就從這里調取數據特別是一些制圖軟件，體積非常大，占用很多空間。
2、locallow是用來存放共享數據，這兩個文件夾下的文件就用優化大師清理，一般都可以清理無用的文件。
3、roaming文件夾也是存放一些使用程序后產生的數據文件，如 空間聽音樂，登入 的號碼等而緩存的一些數據，這些數據優化大師是清理不掉的，可以打開roaming文件夾里的文件全選定點擊刪除，刪除不掉的就選擇跳過，不過當你再使用程序時，這個文件夾又開始膨脹，又會緩存數