its already included, if u are downloading a file from a site u mite have doubts about, then i suggest taking an old ipod, if u have one, plug it in, go into itunes and select the thing where it makes it like a hard disk mode or something, go to disk utility, click the partition tab, click on volume scheme, then select 1 partition, then click options and select the GUID thing, then click ok, and click partition or erase or whatever it says at the bottom. insert the sl disc, start installing it, when it asks u where to install it, click on ur ipod, then when u boot up next time, when the white screen comes on and it makes that noise, hold down option, and select ur ipod, set up ur accounts and what not, then download onto ur ipod, instead of ur macintosh hd, this is safer so u wont screw up ur mac. good luck