Demo machines/devices are ASSUMED to be monkeyed about by the customer. I bought the "demo" Fujitsu Lifebook 280Dx back in '98 because it was the only one left, and they gave me a $300 discount for it. Sure the laptop was riddled with bloatware (someone installed the AOL stuff) but I only needed to chuck in the Recovery CD and wait about 60 minutes for the whole thing to do its job. Hard? Not at all.
Around this time I remember having somewhat a similar experience: I was checking out some nice desktop PC's at Office Depot, and found one that had the shareware version of DESCENT. Oooh, nice! So I proceeded to play on it, until some employee came asking if I needed some help. So I rambled a bit on asking if the graphics card could do 1024x768 and 3D acceleration, knowing this dude would be hoplessly lost on this. (Note: all this info was already in the sticker that these boxen usually have.) So he went away, and I kept on playing.
Lo and behold, he had gone for the manager (?) who I also asked the same thing, but instead of answering me, he proceeded to close Descent (whatever, I had just beaten the Level 7 boss anyway) and tell me "we can't let you play on these PCs". So I did my comeback, "oh well then I can't let you SELL me this computer, I can build one myself!". Oh yes, and duly followed by a complaint in the "Suggestions" box.
Had I been "detained" by a store manager for something like this though, I think said bloke would've been introduced to my juicy little 50kV BOFH-approved TASER Gun!
These days, my fun basically relies on having cmd access, and making small assembly programs that read something like "ALL YOUR PC ARE BELONG TO US" or so.