Snow Leopard theme for Windows 7 (by sagorpirbd)

Download and installation instructions here: Snow Leopard for Windows 7 theme by sagorpirbd
If you run into problems with the free-activator (just click the advertisement) or just want to see what's in there beforehand, you can extract the files yourself.
Extract "Snow Leopard for Win7 Setup.exe" using a RAR-extractor. The password is snhgqzsdhbktin7
Here's a batch file (put in "System Files") to help replacing the system files:

@echo off
SETLOCAL ENABLEEXTENSIONS
if exist backup goto :SKIPBACKUP

:BACKUP
mkdir backup
copy "%windir%\Explorer.exe" backup
copy "%windir%\System32\Shell32.dll" backup
copy "%windir%\System32\ExplorerFrame.dll" backup
copy "%windir%\System32\OobeFldr.dll" backup
pause

:SKIPBACKUP
call :REPLACE "explorer\64 BIT\explorer.exe" "%windir%\Explorer.exe"
call :REPLACE "shell32.dll\64 BIT\shell32.dll" "%windir%\System32\Shell32.dll"
call :REPLACE "ExplorerFrame.dll\64 BIT\ExplorerFrame.dll" "%windir%\System32\ExplorerFrame.dll"
call :REPLACE "Welcome Center\64 BIT\OobeFldr.dll" "%windir%\System32\OobeFldr.dll"
pause
goto :EOF

:REPLACE
echo --- From %~1 to %~2 ---
if not exist "%~1" goto :ERROR
takeown /F "%~2"
Icacls "%~2" /grant Administrators:F
rename "%~2" "%~nx2.old"
copy "%~1" "%~2"
sleep 5
fc /B "%~1" "%~2" || echo ------------- %~2 mismatch ---------------
exit /B

:ERROR
echo Could not find source file!
pause 

There is also a program called "leftsider" which puts the control icons of a window on the left side, just like on a real Mac.