Windows GVim installation can't find plugins

On Windows 10, I have GVim installed to Users\myuser\Vim. I'm using Vundle to handle plugins and it is working fine. But vim isn't finding any of my other plugin files. They're installed (using Vundle) to Users\myuser\vimfiles\bundle. How can I get vim to find them?

I've already tried adding the plugin directory to my rtp in _vimrc, but no luck. I don't know if this is related, but when I start vim it always starts with the pwd as C:\WINDOWS\System32 rather than the directory Vim is installed in.

Here is the opening part of my _vimrc:

set nocompatible
"source $VIMRUNTIME/vimrc_example.vim
source $VIMRUNTIME/mswin.vim

au! BufWritePost $MYVIMRC nested source $MYVIMRC

filetype off " required

set rtp+=%HOMEPATH%\Vim\vimfiles\bundle\Vundle.vim
set rtp+=%HOMEPATH%\Vim\vimfiles
call vundle#begin()
let g:vundle#bundle_dir='vimfiles\bundle'

Plugin 'VundleVim/Vundle.vim'

" basic editing functions------------------------------------
Bundle 'tpope/vim-abolish'
Bundle 'Lokaltog/vim-easymotion'
Bundle 'camelcasemotion'
Bundle 'rename'
Bundle 'tpope/vim-repeat'
Bundle 'scrooloose/nerdcommenter'
Bundle 'surround.vim'
Bundle 'gundo'
Bundle 'YankRing.vim'
Bundle 'vim-multiple-cursors'
Bundle 'guifontpp.vim'
" gui---------------------------------------------------------
Bundle 'vim-airline/vim-airline'
Bundle 'vim-airline/vim-airline-themes'
Bundle 'qpkorr/vim-bufkill'
Bundle 'drmikehenry/vim-fontsize'
" project management------------------------------------------
Bundle 'xolox/vim-session'
Bundle 'TaskList.vim'
" code completion and symbols---------------------------------
Bundle 'snipmate'
Bundle 'supertab'
Bundle 'scrooloose/syntastic'
Bundle 'majutsushi/tagbar'
Bundle 'Valloric/YouCompleteMe'
"Bundle 'Shougo/neocomplete.vim'
Bundle 'Shougo/context_filetype.vim'
" utilities---------------------------------------------------
Bundle 'tlib'
Bundle 'AnsiEsc.vim'
Bundle 'vim-misc'
Bundle 'WebAPI.vim'
" search and navigation---------------------------------------
Bundle 'Shougo/unite.vim'
Bundle 'ack.vim'
Bundle 'kien/ctrlp.vim'
Bundle 'scrooloose/nerdtree'
Bundle 'voogle'
" filetypes and code hilighting---------------------------------
Bundle 'SyntaxRange'
" markdown--------------------------------------------------------
Bundle 'vim-pandoc/vim-pandoc'
Bundle 'vim-pandoc/vim-pandoc-after'
Bundle 'vim-pandoc/vim-markdownfootnotes'
Bundle 'vim-pandoc/vim-pandoc-syntax'
" latex----------------------------------------------------------
Bundle 'jcf/vim-latex'
" python---------------------------------------------------------
Bundle 'pychimp'
Bundle 'klen/python-mode'
Bundle 'monotasker/vim_web2py_syntax'
" javascript------------------------------------------------------
Bundle 'itspriddle/vim-jquery'
" html/xml--------------------------------------------------------
Bundle 'closetag.vim'
Bundle 'XML-Folding'
Bundle 'rstacruz/sparkup', {'rtp': 'vim/'}
Bundle 'bonsaiben/bootstrap-snippets'
" css---------------------------------------------------------------
Bundle 'vim-less'
Bundle 'vim-lesscss'
Bundle 'less-syntax'
Bundle 'css_color.vim'
" svg---------------------------------------------------------------
Bundle 'svg.vim'
" colorschemes ---------------------------------------------------
Bundle 'chriskempson/base16-vim'
"Bundle 'solarized'
Bundle 'flazz/vim-colorschemes'
Bundle 'vividchalk.vim'
Bundle 'Lokaltog/vim-distinguished'
Bundle 'altercation/vim-colors-solarized'
" color utilities ---------------------------------------------------
Bundle 'colorv'
Bundle 'galaxy.vim'
Bundle 'guicolorscheme.vim'
Bundle 'KabbAmine/vCoolor.vim'
" version control ---------------------------------------------------
Bundle 'tpope/vim-git'
Bundle 'tpope/vim-fugitive'
" snippets ----------------------------------------------------------
Bundle 'monotasker/web2py-snippets'

" All of your Plugins must be added before the following line
call vundle