See here how to move iTunes library to another computer:
http://www.theanswerbank.co.uk/Technology/Comp uters/Question569219.html
And yes, moving it to your laptop is a good idea.
In the above link, see the folder I linked to... documents and settings/username/etc. stuff? Find the iTunes music folder that I mention there on your computer, and right click it and click properties. It'll tell you how much space it's using.
And 86GB is pretty normal for a laptop, still these days.
If you want a cool way to visualise what stuff is taking up all the room, download and use (free) an app called windirstat:
http://windirstat.info/