Hi Chinna,
I have follow the next steps with out problems to install/update WAS 8 in windows environment. If you download the Fixpack and register repository then internet is NOT needed.
1.- Download IBM Installation Manager (IM)
2.- Update IM
3.- Download WAS binaries (If you have passport avantage/Value Package you can configure to download directly software from IBM->Internet requiered)
4.- Unzip binaries in the same directory.
5.- Register repository (directory where you have unzipped binaries)
6.- Install product from IM.
7.- Download WAS FP
8.- unzip WAS FP
9.- Register repository of WAS FP
10.- From IM update button and then select WAS FP
11.- When finish updating, create profiles.
Hope this helps.
regards,