For this I look to utilities such as AUTORUNS, MSCONFIG, HIJACKTHIS and then look to research each line with a google search.
There is no one answer to the white box as there could be some thousand apps (good, bad, other?) that could do this. The tools I noted are free.
Bob
There is a decent size white box that sits in the middle of my screen. After I log on it doesn't appear for about a minute. Anything by the white box you can't see because it covers everything up. And you can left hand click on it. You can't do anything with it in the way. Please help!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic