I need to remotely access and use my work computer a few times a week. I want to use VNC because of the price. I've used VNC before, mostly on my own network, where it's fast. However, VNC over the internet is incredibly slow. Even at 256 colors and lower, with Aero turned off, it is unbearably slow. I recently used Ammyy Admin to connect to do something requiring a quick reaction time. Ammyy was really fast, with almost no lag, and it was running in full color with Aero on! How can I make VNC faster, like Ammyy is? I'd use Ammyy, but I would probably run into the 15hr/month limit pretty quickly. Any suggestions?

[EDIT] I'm currently using UltraVNC.