Windows 7's useful taskbar is great, but if you don't like waiting for the thumbnails to show up when you hover your mouse over a taskbar item, a simple registry hack will speed things up.
Tech blog How-To Geek highlights the simple registry tweak that improves the speed at which thumbnails appear in the taskbar. Before attempting to edit your registry, it is always recommended to backup your registry beforehand in case anything goes wrong. Windows site How-To Geek has the instructions:
First type regedit into the search box in the Start Menu and hit Enter.
Now navigate to HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerAdvanced and right-click to create a new DWORD. Name it ExtendedUIHoverTime.
Now double-click on ExtendedUIHoverTime, and give it a Decimal value of "1." Click OK, and exit the Registry Editor. Log off [your system]and log back on for it to go into effect.
The same trick can also be used to slow the rate at which thumbnails show up. We've also covered a few other registry hacks that will speed up your Windows taskbar, so give those a look if your taskbar isn't cutting it.