It’s not difficult to find some Mac themes online. The only real difficulty is finding one that actually works! After browsing around the Internet a bit, there were some themes that did not install properly, or at all. Seldom did any themes actually have useful instructions. Another difficulty is finding a theme that didn’t need any secondary software to install it. Giving up, the only really solid theme I found was this Mac OSX Theme.
The visual appearance is about as close to a Mac as you can get. The dock menu at the bottom is impressive, and the appearance of windows, icons, and mouse cursors are bang on. Of course, it will never be exactly like a Mac. By this, I mean that the Start menu (now dragged to the top) is still the Start menu. Conversely, some of the gadgets installed looked a little bit funny in comparison, but the issue is only for those who tend to use Sidebar. Furthermore, you can even further customize this theme with different colour schemes. Best of all, installation was simple, and the theme runs very smoothly.
The only real downside is that you will need WindowBlinds in order to run this theme. On top of that, use of the software isn't free, either. It does run as shareware, so you can use it for 30 days, but after that, you will need to pay $20 USD. At this point, you would need to decide if it’s worth paying just do use a graphic scheme.