Applying Win2003 Serv. Pack 1 returns message that tcpip.sys is in

Win2003 Ent Server, Exch2003 SP1. Service Pack 1 copied over local server.
I launch Service Pack and the following message appear:

"The file c:\windows\system32\drivers\tcpip.sys" is open or in use by
another application. Close all other applications and then click Retry."

Eventvwr error is displayed below.
I alredy restarted the server, no improvement. There is no application
running on the server (other than File System AV which I attempted to stop
and that didn't help either).

Please advise how can I fix this ?

"Event Type: Error
Event Source: NtServicePack
Event Category: None
Event ID: 4373
Date: 11/3/2005
Time: 10:11:48 PM
User: N/A
Computer: My
Description:
Windows Server 2003 Service Pack 1 installation failed.
An internal error occurred.


For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.