You can do a system restore to a point in time before you deleted it or...
1. the Start Menu folder is a "protected operating system file" and must be unhidden in Folder Options in the Control Panel.
2. right click on the start menu folder. it can be founs at C:\Users\your name\Start Menu and select "properties". Look for a previous versions tab.
3. If you find a previous version from step 2 that is dated before the deletion, you can restore that previous version.