The best option for Windows 7 IMO is to install www.classicshell.net - it makes the Search functionality from the Start Menu more intelligent by adding things like substring search and launch frequency tracking (so that it learns to autoselect the programs you use most often).
The main problem with it is that it still relies on the basic search functionality provided by Windows so:
It's usually slow to react the first time you use it after a Windows restart.
It can only launch system settings / Control Panel shortcuts or the shortcuts it can find in the Start Menu (Programs etc.) - it doesn't look at your list of installed programs (the former "Add/Remove Programs"). The way I "teach" it new programs is by manually creating shortcuts for them in an out-of-the-way folder in Programs/Accessories/CustomShortcuts.
The main reason I prefer it to Launchy and Executor and Enso Launcher is that it can be accessed with a single key-press, typically the Super key, after which I can immediately start typing what I'm trying to launch, which is exactly what I do with Synapse on Linux. Compared to Synapse though, I sorely miss the ability to type mathematical expressions directly in the search box and have them calculated live.