Its amazing how the obviously good products are over looked.
Ive used total commander, and although it is a 'bit' better than opus (which is not free source),
Powerdesk is by *far* the best file manager for win32
http://www.v-com.com/product/pd_ind.html

someone had mentioned vi for windows, you have to be at least 18 to use it ;)
vim.org