I've been meaning to do a write up on tools for applying patches on Windows but haven't had a chance. For now I'll just leave it at this list.
GNU Commandline Utilities
All of these can be downloaded as setup files that install into
C:\Program Files\GnuWin32 (by default) so you'll want to add
C:\Program Files\GnuWin32\bin to your system path.
DiffUtils - show differences between files
CoreUtils - GNU file, shell and text utilities
CygUtils - miscellaneous utilities including dos2unix and unix2dos (which you'll need to convert the line endings to keep patch happy)
Patch - apply a diff file to an original
Wget - retrieve files from the WWW
WinMerge - visually compare the text files