That sounds to me like you are frequently re-installing Windows, and then having to re-download updates. If so, then perhaps you need to be looking at why you need to re-install so often.
But that's another matter.
You might want to consider taking an image of your whole installation with something like Acronis True Image. If you don't want to pay for the imaging software, you could consider free cloning software like DriveImage XML. Whilst I use Acronis True Image and am very satisfied with it, I have never used DriveImage XML but I understand from others it is a good utility.
Finally, if you are looking just to backup your system with all the latest Windows Updates, then you could lookup "Slipstreaming".
I hope that helps.
How to backup the system files to another or portable drive ? I think having this type of back-up will ease the problem of frequent downloading the updates of softwares, antiviruse difinitions etc. on formating of Hard-drive. I am using Windows XP SP2.