Some notes from the day when the loopback aliases quit working 
on a Windows NT system, months after I had installed it and it had
been working all that time.

  For some reason, some files got erased and I wound up copying
them over from some other NT system.  The problem was figuring it
all out, which took days.

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NDIS = Network Device Interface Specification
     = Microsoft's Standard for Driver Design

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In the C:\WINNT\system32\drivers directory, there are 3 files

(I couldn't tell what the following 3 lines were, so I just copied
 them here verbatim, attempting to line things up as they were on
 the scrap of paper, without any editorial comments.)
  - NDIS.SYS     --sys\ndis.dbg      k\lib\i386\ndis.sys
  - NDISTAPI.SYS -- " \ndistapi.dbg  b\i386\ndistapi.sys
  - NDISWAN.SYS  -- " \ndiswan.dbg   lib\i386\ndiswand.sys

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C:\WINNT\system32\drivers\loop.sys -> Microsoft loopback Network 
                                      NDIS Driver
V4 Build 1381  S.P.5