I have been using Windows XP for a long time now but the day I started using Windows 7, it interested me more than XP. It has several better features and one such is the Taskbar thumbnail view of the different applications installed in the system.
This tool called Windows 7 Taskbar Thumbnail Customizer will allow you to resize & tweak the Windows 7 taskbar thumbnails left & right, in & out. The tool is capable of doing many things like changing the size of the thumbnail, its spacing, top, bottom, left, right margins and mouse delay time too.
The tool is very easy to use and using this you can easily change the margins or the spaces between the thumbnails of the icons. Customizing Windows is quite easy now.