The Windows 7 taskbar is awesome, but its preview thumbnails are a tad small. If you want a closer preview of your open windows, this registry hack lets you customise their size.
Just click the Start menu, type
regedit in the search box, and start up the Registry Editor. Then, navigate to
HKEY_CURRENT_USER/Software/Microsoft/Windows/CurrentVersion/Explorer/Taskband. Right-click in the right-hand pane of the editor, and choose New > DWORD (32-bit) Value. Name it
MinThumbSizePx. Double-click on it to edit it, and type in the value you want (the image above uses a value of 400 — you may need to play around with it to find one you like). Click OK, then log out of Windows. When you log in, you should find your taskbar thumbnails are the size you want. Of course, you can always use a program like previously mentioned Windows 7 Taskbar Thumnbail Customizer to do this, but this is a quick way to do it without any extra software.