UltraVNC 1.0.8.2 is a free, remote desktop application that allows a user to view and control the screen of another computer. I've been using this for years, and using it more often since I have an HTPC connected to my family HDTV. Who wants to stop their TV program so I can change settings on my computer? With UltraVNC, you don't have to interrupt other people's programming: just log in securely and away you go.

Special Instrucions for Windows 7

The computer you want to control must have UltraVNC installed as a service on a Windows machine. I found excellent instructions at sevenforums. Note that these instructions are talking about 1.0.5 but it uses the same version of the video hook driver (aka mirror driver). This can be downloaded with the install program during setup. Follow the instructions, making sure you reboot after install and ignore the warning that the video hook driver is not working: apparently it is. Here are the same instructions, updated to the latest stable release, 1.0.8:

Download uVNC 1.0.8.2 Full for win32 or x64
UltraVnc download manager

Install VNC
Enter your admin password for VNC
Uncheck 'Remove Aero (Vista)'
Uncheck 'Remove Wallpaper for Viewers'

Install Video Hook Drivers (if you didn't check the 'download mirror drivers' option during setup)
http://sc.uvnc.com/drivers.zip
Extract to folder 'Drivers' anywhere.
Right click setupdrv, Create Shortcut
Properties of shortcut
Add ' install' to end of the target box
Click Advanced
Check 'Run as administrator'
OK, OK
Double-click the setupdrv - shortcut
Accept installing the driver
Restart

In start menu, under UltraVNC, right click 'Edit Settings' click Run as Administrator
In 'Screen Capture' tab,
Check off:
Poll Foreground Window
Poll Window Under Cursor
System HookDll
Video Hook Driver (Check the video hook driver will report it's not active but it really is.)
Apply
OK
Restart and check previous setting to make sure they stick.

Download the 1.05.6 uVNC Viewer in 32 or 64 bit accordingly and select 'Ultra' mode for your connect speed.

For best performance through VNC over LAN, tweak the following Windows 7 visual settings:

Right click My Computer, Properties, Advanced tab, Performance->Settings

Check only the following options (you can uncheck some options to improve remote internet viewing):
Enable Aero Peek
Enable Desktop Composition
Enable Transparent Glass
Save taskbar thumbnail previews
Show thumbnails instead of icons
Show window contents while dragging
Smooth edges of screen fonts
Use drop shadows for icon labels on desktop
Use visual styles on windows and buttons

And remember, set your power options in Windows 7... the default is to sleep the computer after 20 mins.

I'm able to web browse through it and it seems local in responsiveness... quite impressive compared to other OS's for VNC.