It's easy to find, it's just done a little differently than before.
To get to the defragger, click on the Start button, and type in "disk defragmenter" in the search window at the bottom. "Disk Defragmenter" should appear at the top of the search results
It's an "okay" defragger program but I highly recommend using Raxco's PerfectDisk. In my opinion it's the best on the market. However you do have to pay for it.
If you want a better one than the Windows 7 version, but want a free one try Defraggler.
http://www.piriform.com/defraggler
A review from
PC World
"Defraggler will show you all your fragmented files. You can click one to see where on the disk its various pieces lie, or defragment just that one. This can be useful when dealing with very large, performance critical files such as databases... Piriform Defraggler is free, fast, marginally more interesting to watch than the default, and has useful additional features. What's not to like?"