any idea how to update python PIP on a windows box?

pip install --upgrade pip doesn't work because the windows FS is brain damaged and won't let you delete an open file.

I've tried setting my environment to the virtualenv that I want to update and then running from a different pip, but that fails with:

(jm) E:\python\jm>c:\Python26\Scripts\pip install --upgrade pip
Downloading/unpacking pip
  Running setup.py egg_info for package pip
    warning: no previously-included files matching '*.txt' found under directory 'docs\_build'
    no previously-included directories found matching 'docs\_build\_sources'
Installing collected packages: pip
  Found existing installation: pip 0.7.1
    Uninstalling pip:
      Successfully uninstalled pip
  Running setup.py install for pip
    warning: no previously-included files matching '*.txt' found under directory 'docs\_build'
    no previously-included directories found matching 'docs\_build\_sources'
    Installing pip-script.py script to c:\Python26\Scripts
    Installing pip.exe script to c:\Python26\Scripts
    Installing pip.exe.manifest script to c:\Python26\Scripts
    Installing pip-2.6-script.py script to c:\Python26\Scripts
    Installing pip-2.6.exe script to c:\Python26\Scripts
    Installing pip-2.6.exe.manifest script to c:\Python26\Scripts
Exception:
Traceback (most recent call last):
  File "c:\Python26\lib\site-packages\pip-0.7.1-py2.6.egg\pip\basecommand.py", line 120, in main
  File "c:\Python26\lib\site-packages\pip-0.7.1-py2.6.egg\pip\commands\install.py", line 165, in run
  File "c:\Python26\lib\site-packages\pip-0.7.1-py2.6.egg\pip\req.py", line 1251, in install
  File "c:\Python26\lib\site-packages\pip-0.7.1-py2.6.egg\pip\req.py", line 466, in commit_uninstall
  File "c:\Python26\lib\site-packages\pip-0.7.1-py2.6.egg\pip\req.py", line 1549, in commit
  File "c:\Python26\lib\shutil.py", line 216, in rmtree
    rmtree(fullname, ignore_errors, onerror)
  File "c:\Python26\lib\shutil.py", line 216, in rmtree
    rmtree(fullname, ignore_errors, onerror)
  File "c:\Python26\lib\shutil.py", line 221, in rmtree
    onerror(os.remove, fullname, sys.exc_info())
  File "c:\Python26\lib\shutil.py", line 219, in rmtree
    os.remove(fullname)
WindowsError: [Error 5] Access is denied: 'c:\\users\\mark\\appdata\\local\\temp\\pip-gvsove-uninstall\\python26\\scripts\\pip.exe'

Storing complete log in C:\Users\mark\AppData\Roaming\pip\pip.log

(jm) E:\python\jm>dir c:\Users\mark\AppData\Local\temp\pip-gvsove-uninstall\python26\scripts
 Volume in drive C has no label.
 Volume Serial Number is 74E4-FE9F

 Directory of c:\Users\mark\AppData\Local\temp\pip-gvsove-uninstall\python26\scripts

12/07/2010  11:32 AM    <DIR>          .
12/07/2010  11:32 AM    <DIR>          ..
05/14/2010  05:54 PM             7,168 pip.exe
               1 File(s)          7,168 bytes
               2 Dir(s)  22,824,603,648 bytes free

(jm) E:\python\jm>del c:\Users\mark\AppData\Local\temp\pip-gvsove-uninstall\python26\scripts\pip.exe

I'm hoping someone else has figured out a way around this. Its no problem on linux....