Since I have installed win7, by default automaticcaly windows update till date. Now before formatting my PC, I want to make boot DVD with all till date updates. How Can I?
You cant use installed updates to create an integrated dvd, you need either all the individual hotfixes or the service pack. Slipstreaming with SP1 is your best option.
SP1 has all of the updates since Win7 was released, plus patches and bugfixes. Your Win7 installer should have it slipstreamed to save a lot of updating.