You probably have the option to highlight searched text on. You can override the defaults in the vimrc by making a .vimrc file in you home directory. Here's one I nabbed from one of the servers here at school that I use. Notice I commented out the lign to highlight search strings.
" An example for a vimrc file.
" Maintainer: Bram Moolenaar <Bram@vim.org>
" Last change: 2002 May 28
" To use it, copy it to
" for Unix and OS/2: ~/.vimrc
" for Amiga: s:.vimrc
" for MS-DOS and Win32: $VIM\_vimrc
" for OpenVMS: sys$login:.vimrc
" When started as "evim", evim.vim will already have done these settings.
rogname =~? "evim"
" Use Vim settings, rather then Vi settings (much better!).
" This must be first, because it changes other options as a side effect.
" allow backspacing over everything in insert mode
set autoindent " always set autoindenting on
set nobackup " do not keep a backup file, use versions instead
set backup " keep a backup file
set history=50 " keep 50 lines of command line history
set ruler " show the cursor position all the time
set showcmd " display incomplete commands
set incsearch " do incremental searching
" For Win32 GUI: remove 't' flag from 'guioptions': no tearoff menu entries
" let &guioptions = substitute(&guioptions, "t", "", "g")
" Don't use Ex mode, use Q for formatting
map Q gq
" This is an alternative that also works in block mode, but the deleted
" text is lost and it only works for putting the current register.
"vnoremap p "_dp
" Switch syntax highlighting on, when the terminal has colors
" Also switch on highlighting the last used search pattern.
if &t_Co > 2 || has("gui_running")
" Only do this part when compiled with support for autocommands.
" Enable file type detection.
" Use the default filetype settings, so that mail gets 'tw' set to 72,
" 'cindent' is on in C files, etc.
" Also load indent files, to automatically do language-dependent indenting.
filetype plugin indent on
" For all text files set 'textwidth' to 78 characters.
autocmd FileType text setlocal textwidth=78
" When editing a file, always jump to the last known cursor position.
" Don't do it when the position is invalid or when inside an event handler
" (happens when dropping a file on gvim).
autocmd BufReadPost *
\ if line("'\"") > 0 && line("'\"") <= line("$") |
\ exe "normal g`\"" |
endif " has("autocmd")