Hi,
Welcome to Microsoft community forums and thank you for posting the question. As per the description, you are unable to find the 'Run' option in start menu. Let's perform few steps to restore the 'Run' option.
Method 1:
1. Open the Start Menu.
2. Right Click on a empty space on the Start Menu and select
Properties.
3. Click on the Start Menu Tab and click on Customize.
4. Tick the Run Command and OK.
Method 2:
Click Start > Programs > Accessories >
Run.
To add it to the Start Menu:
Right-click your Taskbar > Properties >
Start Menu > Customise > Scroll down > Add
run command > Etc.
For more information check out the link given below:
http://windows.microsoft.com/en-US/windows7/Customize-the-Start-menu
Also you can open the runline window by holding the 'Windows key' + R. This will bring up the run window even if it hides from the start menu.
Hope this information helps. If you face any more issues while working with Windows do post on Microsoft Community Forum.