Where I find all thing under one roof ?

"Online" and "under one roof" do not belong together. Even "search" is handled by a dozen or more sites.

The first place to go to search for something is google.com and the first place to go to buy something is amazon.com

But amazon does not have everything, so the second place to go is overstock.com and google will link you to a lot of other options. The internet is bigger than you think, even if you think real big.

BTW you didn't ask, but the first place to go for any software is tucows.com and for any computer equipment it's tigerdirect.com