Python WMI调用不能在Windows 7下运行

这是我的代码：

from win32com.client import GetObject

def get_printers(computer):
    """ Get a list of printers from the specified computer name. """
    wmiservice = GetObject(r"winmgmts:{impersonationLevel=impersonate}!" + computer + r"rootcimv2")
    return wmiservice.ExecQuery("Select * from Win32_Printer")

for printer in get_printers("ps2"):
    print printer.Name

这在Windows XP下运行良好.但是如果我在Windows 7下运行它会失败：

Traceback (most recent call last):
  File "C:Python27Libsite-packagesPythonwinpywinframeworkscriptutils.py",line 325,in RunScript
    exec codeObject in __main__.__dict__
  File "C:Python27sampletemp2.py",line 8,in <module>
    for printer in get_printers("ps2"):
  File "C:Python27sampletemp2.py",line 5,in get_printers
    wmiservice = GetObject(r"winmgmts:{impersonationLevel=impersonate}!" + computer + r"rootcimv2")
  File "C:Python27libsite-packageswin32comclient__init__.py",line 72,in GetObject
    return Moniker(Pathname,clsctx)
  File "C:Python27libsite-packageswin32comclient__init__.py",line 87,in Moniker
    moniker,i,bindCtx = pythoncom.MkParseDisplayName(Pathname)
com_error: (-2147024891,'Access is denied.',None,None)

我在Win 7中尝试了所有我能想到的：禁用防火墙(无病毒扫描程序),确保启用DCOM,确保启用WMI以及禁用UAC.任何帮助都会受到高度赞赏.

注意：我在Windows 7 Ultimate x86(和Windows XP SP3)下使用Python 2.7.1和pywin32 build 215.