Is there any free/paid Windows emulator for Mac OS X?
Wine
You could try Wine and use the  Winebottler frontend for installing common Windows software.
With Wine isn't 100% compatible with all windows programs, so consider yourself lucky if all your applications work.
Virtualbox
Virtualbox is a PC virtualization software. You'll need to install Windows as a &quot;Guest operating system&quot;, which requires a Windows license.
Virtualbox is compatible with all Windows software, but has limited support for hardware 3D acceleration.
Boot Camp
For 3D games you'll need to use Boot Camp.