Could i search and download ubuntu's packages using windows OS. If can then please tell me, whats the website. many thanks.
I suppose you want to download packages that will be later installed on a Ubuntu machine. The official Ubuntu repository can be accessed over the net at http://packages.ubuntu.com/. You can download .deb packages in that website and install it with
dpkg -i on the Ubuntu system.
All of the ubuntu packages? Sure, just download the disk image and extract it.
You can search the packages here.
Once you're on the package page, you can navigate between versions (lucid, precise, quantal, raring) on the top right and you'll find the .deb download links on the bottom. (click on your architecture and choose a mirror to download from)