I'm bringing an actual desktop computer with me to Japan. It's kind of a half-size case. I don't have a monitor, since I figured I could just buy one in Japan without having to use up valuable packing space. I have a small amount of pirated software, though 95% of it is legitimately bought. It also has glass sides, so you can see the "guts" of the computer. That could save me some trouble, since they won't have to actually open it up to see if there's any explosive material or drugs in it.
Still, I'd sooner leave my pirated programs and mp3s ON my computer than put them on a dvd... However, everyone I've talked to says that they probably won't even give your CDs or DVDs a second glance.
But the question is, are they a bit more thorough with dektops than laptops?
I don't have a monitor with me, so all they would be able to see is the blue lights inside and the fan. I'm also bringing a LOT of CDs with me. Mostly purchased games, software drivers, the windows CD, some music CDs, etc, plus a few DVD-RWs, 4/5 of them blank. I'll be leaving my 613 megs of mp3 files in the "My Music" folder, and my anime fansubs in the movie folder.
Also, just like in the states, I don't think you can get in trouble for just having MP3 files. For all they know, you may actually have all the CDs at home, and just wanted to save space.