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Option Explicit 
Dim ret As String 
Dim jj As String 
Dim winsys As String 
Private Declare Function GetSystemDirectory Lib "kernel32" Alias "GetSystemDirectoryA" _ 
 (ByVal lpBuffer As String, ByVal nSize As Long) As Long 
Private Declare Function GetWindowsDirectory Lib "kernel32" Alias "GetWindowsDirectoryA" _ 
 (ByVal lpBuffer As String, ByVal nSize As Long) As Long 
 Private Const max_path = 260 
 'Private Const max_path1 = 261 
Private Sub Command1_Click() 
 Dim ssave As String 
 ssave = Space(255) 
 ret = GetSystemDirectory(ssave, 255) 
 jj = Len(Trim(ssave)) 
 winsys = Trim(Mid$(ssave, 1, jj - 1)) 
 MsgBox winsys 
End Sub 
Private Sub Command2_Click() 
 Dim sysdir As String 
 Dim chrlen As Long 
 Dim windir As String   
 'sysdir变量要给足了空格 
 sysdir = Space(max_path) 
 chrlen = GetSystemDirectory(sysdir, max_path) '将系统路径保存在字符串sysdir中,字符串最大长度为260     
 If chrlen > max_path Then chrlen = GetSystemDirectory(sysdir, chrlen)   
 'chrlen是返回字符串的实际长度 
 sysdir = Left(sysdir, chrlen)   
 '------------------------------------------------- 
 '取windows路径 
 windir = Space(max_path) 
 chrlen = GetWindowsDirectory(windir, max_path) 
 If chrlen > max_path Then chrlen = GetWindowsDirectory(windir, chrlen) 
 windir = Left(windir, chrlen) 
 MsgBox "system的路径为: " & sysdir 
 MsgBox "windows的路径为: " & windir 
 MsgBox "当前系统的盘符为:" & Left(windir, 1) 
End Sub