free application to view microsoft document and use iphone as USB key

I have more than 10G space, I want to use iphone as USB key, I download a free app. USB key, but it can only view *.html in root directory, anyone know other free app to send my 250Mb project document to iphone,? I try total commander, but I dont know which sub folder of my iphone I should put my project document.
also anyone know how to browse and edit word, excel, ppt in iphone, any free app?
my ibooks can only view PDF.?
anyone knows any free app like windows explorer in iphone, so we can can touch any microsoft office document and open it.?
in iphone 4, what are the file type for video and movie, anyone know how to open *.avi in iphone?
iOS 4