I found the "solution".. It wasn't tough as I thought it end up as :-D
For those who are searching for why Windows Vista and above wont be able to open Hlp Files :
From this article : http://support.microsoft.com/kb/917607
“Microsoft stopped including the 32-bit Help file viewer in Windows releases beginning with Windows Vista and Windows Server 2008. To support customers who still rely on legacy .hlp files, the Microsoft Download Center provides WinHlp32.exe downloads for Windows Vista, Windows 7, Windows Server 2008, and Windows Server 2008 R2.”
How-ever, winhlp32/64.exe is available for download explicitly from here : http://www.microsoft.com/downloads/en/details.aspx?FamilyID=258aa5ec-e3d9-4228-8844-008e02b32a2c&displaylang=en
Another option is probably to convert the .hlp files to .chm files. Microsoft does provide some rudimentary tools to convert from .hlp to .chm format; how-ever apparently, the output won’t be polished enough.