Where is Xcode located on the hard drive?

Xcode and the rest of the Apple Developer tools get installed to /Developer

Simply open the Finder (Mac face in bottom left of the Dock) and Choose:

Macintosh HD/Developer/Applications/Xcode.app

I think it installs somewhere under /Developer or something like that... But you can always use Spotlight to find and start it:

Press Command-Key (the one next to Space with the funny sign) + Space and type xcode. Press enter and it should start.

You might also consider installing Quicksilver, LaunchBar, or Butler — all three are quick-launchers which allow you to press something like Ctrl-Space and type an abbreviation of the app name, so entering 'xc' will get you XCode.

It's the same as you're getting with Spotlight, but you can do other useful things that Spotlight doesn't make so easy: if you've entered an abbreviation for a document, for example, you can hit Tab and enter the abbreviation for the app you want to open it with.

Quicksilver and Butler are free; LaunchBar costs money. Butler has the best icon, IMHO :)

Unfortunately I can't give you direct links as my reputation's too low and I'm not allowed more than one — but you can find them all by searching at http://macupdate.com…

Use Spotlight, and just type xcode. You will see it.