In Windows 7 when you hover your mouse over any item on the Taskbar, a preview is displayed. The size of the preview depends on how many items you have in that item group, the more the item bigger is the preview but still size of the individual item remains small.
This leads to a problem that you cannot see it in the preview and you need to mouse hover the preview to bring the original window in the front. Though this solves the problem but if you want a bigger preview to figure out things, Windows 7 Taskbar Thumbnail Customizer is a good utility you can use.
Like you can see above Size of the thumbnail has increased when compared to last image. Features of this tool:
- Change Thumbnail Size
- Adjust Spacing.
- Change Margin
- Change delay time.
This tool was developed by Kishan and you can download and read more on his post.