VIBHA KHOT,
Please try the following to see if this will allow the activation process to complete:
1) Click the START button.
2) Click ALL PROGRAMS.
3) Look at the list of your installed programs and find INTERNET EXPLORER.
4) Point the mouse cursor over top of INTERNET EXPLORER until it is highlighted and click the RIGHT-MOUSE button and choose “RUN AS ADMINISTRATOR” from the menu.
5) You will be prompted by a Windows Vista dialog box, and I want you to choose “ALLOW”. This will allow IE to start with administrator privileges.
6) In the new Internet Explorer session, manually type or copy this URL http://www.microsoft.com/genuine (again, make sure it's the new instance of IE that opened as “Administrator”.
7) Once the /genuine web site loads in the new IE browser. Click the “VALIDATE OFFICE” button.
What happened? Are the results different? Please re-post here should you need further assistance. Thank you.
I hope this has helped,
Lori MS