Tested OS : Winodws2000, Windosws98, WindowsNT SP6 and WindowsXP rci japanese.
Tested build : b83 j2re-1_4_0-beta3-bin-b83-win-i-11_oct_2001.exe
               b84 j2re-1_4_0-beta3-bin-b84-win-i-20_oct_2001.exe
                   j2re-1_4_0-beta3-bin-b84-win-20_oct_2001.exe
                   j2sdk-1_4_0-beta3-bin-b84-win-20_oct_2001.exe

I found that the number of installed dll file is different between b81 and b83.

NPJava11.dll, NPJava12.dll, NPJava32.dll and NPJP140.dll file, they are not installed under Netscape6\Plugins directry using J2SDK/J2RE installer for windows.

After installing j2sdk/j2re b83 and b84:
\Program Files\Netscape\Netscape6\Plugins\npoji610.dll

After installing j2sdk/j2re b81:
\Program Files\Netscape\Netscape6\Plugins\npoji610.dll
                                         \NPJava11.dll
                                         \NPJava12.dll
                                         \NPJava32.dll
                                         \NPJPI140.dll

Some NPxxxx.dll files are not installed properly under Netscape6's plugins directry.

Lacking NPxxxx.dll files on Netscape6's plugin directry are installed correctry under other Netscape's plugin directry (ex.Netscape comunicator4.7).

After installing b84, Communicator4.7's plugins directry :
\Proguram Files\Netscape\Communicator4.7\Program\Plugins\npoji610.dll
                                                        \NPJava11.dll
                                                        \NPJava12.dll
                                                        \NPJava32.dll
                                                        \NPJPI140.dll

Lacking NPxxxx.dll files(NPJava11.dll, NPJava12.dll, NPJava32.dll, NPJPI140.dll) needs to be installed under Netscap6's plugin directry.


* NOTE *
  This problem was described in #4514617.
  However, as this problem is not original problem of #4514617,
  I filed this as a separate bug.