Where is the .vimrc file

Why not use tabs (introduced in Vim 7)? You can switch between tabs with :tabn and :tabp, With :tabe <filepath> you can add a new tab; and with a regular :q or :wq you close a tab. If you map :tabn and :tabp to your F7/F8 keys you can easily switch between files.

If there are not that many files or you don't have Vim 7 you can also split your screen in multiple files: :sp <filepath>. Then you can switch between splitscreens with Ctrl+W and then an arrow key in the direction you want to move (or instead of arrow keys, w for next and W for previous splitscreen)

As has been pointed out in a couple of other answers, the preferred method now is NOT to use smartindent, but instead use the following (in your .vimrc):

filetype plugin indent on
" show existing tab with 4 spaces width
set tabstop=4
" when indenting with '>', use 4 spaces width
set shiftwidth=4
" On pressing tab, insert 4 spaces
set expandtab

set smartindent
set tabstop=4
set shiftwidth=4
set expandtab

:help smartindent

:help auto-setting

:set all

:help C-indenting