Apple - PC to Mac - Remote Desktop

VNC

Recent versions of Mac OS X include a VNC server built-in, analogous to Microsoft's Remote Desktop Server (included in Windows). This can be accessed via the System Preferences > Sharing > Apple Remote Desktop option.

There are various free VNC clients available for Windows, most notably RealVNC.

While there are other options, VNC benefits from being a very mature graphical remote-access protocol with official support from Apple and good-quality client programs.

I've tried them all and RealVNC is the best by far. Anything else either lacks important functionality or lags miserably. I recommend you try them all though and decide for yourself; it really comes down to what level of remote control you're looking to have.

This is a full list I found on Wikipedia comparing remote desktop software.