I have a previously installed version of Norton Internet Security.
When installing Norton Internet security 2005, loading will not
proceed because when initializing, message appears " Norton Internet
Security unistallation has failed". I have already tried to remove old
version via add/remove programs but it does not remove program.
Help!???

this will resolve your issue

STEP 1)got to this web site and run this file in
ftp.symantec.com/misc/consumer/nis/nis2005XP_reg_removal.reg if you
are using XP or 2000
or 
ftp.symantec.com/misc/consumer/nis/nis200598_reg_removal.reg if you
are using Win 98 or ME
STEP 2) got to Start-->Run-->%temp% and remove all the temporary files
STEP 3)editing the registry
      a)first make a backup of the registry
      b)find this key in the registry
KEY_LOCAL_MACHINE\SOFTWARE\Symantec and  delete the symantec folder
      c)do the same thing for this key HKEY_CURRENT_USER\Software\Symantec
STEP 4)deleting the symantec folders from the hard drive
       a)delete the following folders symantec and norton folders
      NOTE: "if you do not see the application data folder got to
folder options and select show hidden files"
for XP2000 c:\documents and settings\all users\application data\symantec
for 98ME c:\windows\all users\application data\symantec
        c:\programe files\norton internet ecurity
        c:\programe files\symNRTDRV
        c:\programe files\norton antivirus
        c:\program files\common files\symantec shared
STEP 5) Do a clean boot
         Clean boot for WIn XP
       a)Start-->run__Msconfig__> General. under general select
"SELECTIVE STARTUP" and uncheck "PROCESS SYSTEM.INI, WIN.INI AND LOAD
STARTUP ITEMS"
      got to the "SERVICES" tab and put a check mark next to "HIDE ALL
MICROSOFT SERVICES" and click on "DISABLE ALL" CLICK ON oK AND RESTART
       for WIN98
       MSCONFIG-->GENERAL-->SELECTIVE STARTUP and uncheck "LOAD
STARTUP GROUP ITEMS" and click on OK and restart

STEP 6)download and run msicuu2.exe utility which can be found in
www.tinyurl.com\42ul9
this is the windows utility file, open this file from start menu and
remove all entries pertaining to cc,symantec and norton
      
      download and run windows scrip 5.6 for XP/200 www.tinyurl.com\ar31
      for win 98/ME www.tinyurl.com\8bhn
restart the comp and you can install NISwithout any problems