Like Laptop or Notebook. The difference in this case being that a "Cracktop" is a laptop or notebook in which usually the only piece of legitimate software contained on the hard drive of the laptop is the OS that is built into the computer as standard.
Usually even then, after countless re-boots, viruses and continued anger at manufacturers for bundling "useless ware" into the factory configuration of a computer, a user will one day finally get so pissed off, that even the OS becomes an illegally downloaded copy (which is usually better for your computer anyway), resulting in a complete "Cracktop".
"I'm too embarassed to admit to all my friends and colleagues that my laptop contains little or no legitimate software on its hard drive. It's a cracktop"
"Why do I download from rapidshare? Even though that game only costs a few bucks from the bargain bin? 'Cause this is a cracktop get used to it"
"Man my comp is just a total cracktop now, that blue edition of microsoft office was just too easy to install. Counter Strike online is off the wall its so goddamn cracked"
"just get a cracktop, after u bought your laptop bring it round and i'll sort eeeeverything out"
"No money? Gotta go university? Need microsoft office? cracktop it, so you don't have to live off beans on toast"