Hello Pallavi!

First, You should set environment variables (Control Panel|System|Advanced|Environment variables):
1) QMAKESPEC. It should be win32-msvc2005
2) QTDIR. It is hold a path to Qt dir.
Note: The install path must not contain any spaces or Windows specific file system characters.
3) PATH. Add to this one %QTDIR%\bin;

Than you should:
1) Run Visual Studio command prompt. This is usually done by selecting Microsoft Visual Studio 2005|Visual Studio Tools|<Command Prompt> from the Start menu.
2) Go to your "hello world" project's dir. (by means Visual Studio command prompt)
3) Run qmake
4) Run nmake

It should work!

BWT: Do you have installed SP1 for Visual Studio 2005?