When you search for something in the start menu windows vista search not only in start menu but also search in all index include files from hard drives.
this makes it slow , so we need to do something to make windows vista search only in the start menu
to do that

1-open Register Editor (start menu then run type regedit)
2-navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
3-find the key Start_SearchFiles then right click and select modify
4-change the value to 0
5-reboot your computer