By default, icons on the start menu are large in windows. Decreasing the size of the icons in the start menu is very necessary for people who use too many programs. The main reason why you should decrease the size of start menu icons is that, decreasing the size of the icons increases the number of programs displayed on the recently used programs list.
Another reason being that small icons look more professional than large ones.
How to do it:
1. Right click on the start menu.
2. From the right click drop down list, click properties.
3. On the Taskbar and Start Menu Properties, Check that the Start Menu tab is selected initially (if not, select the Start Menu tab).
4. Now, click on the customize next to the start menu option (not the customize button next to the classic start menu option).
5. Now, in the General tab, select the small icons option under the section Select an icon size for programs.
6. Click OK on the Customize Start Menu dialog box.
7. Finally click OK on the Taskbar and Start Menu Properties dialogue box.
Now click the start menu and you should be able to see small icon in the start menu.