I've seen MUCH worse....
A PC left in a barn area that became infested by a small bee hive (and was STILL WORKING!). The farmer brought it in to our shop for service to have us clean out the "mess" inside the case as part of his free "annual cleaning" as covered under his waranty. He neglected to tell my staff it was bee infested before one of them got stung when he went to pick it up and move it to our back counter after doing an initial systems test. Poor kid picked the tower up as one normally would, one hand on front, one hand across power supply vent in back, but the fan vent was the bees way in and out of the case... He dropped it instantly, causing the side cover to come off and causing some significant damage to the case, a few more bees came out. Fortunately, most of them seemed to have evacuated the case on the way to our shop in the back of the pickup the guy drove.
We had to wrap in in serveral layers of garbage bags, and we used a pack of printable stickers to make some bio-hazard signs. Naturally we refused the cleaning service, and marked his waranty as void citing "unsatisfactory environmental conditions for PC placement and use" He was none too thrilled and threatened to sue the store. This was quickly abated when we threatned to countersue for failure to warn our employees of an eminent danger. 2 of my other staff were so allergic to bees and fire ants that they carry eppy pens 24x7, and if one of them picked up that case instead of the poor kid who did, it would have been a rush to the emergency room not a sore thumb.
We suggested the farmer buy a toughbook to use in his barn instead of a desktop PC, but of course, someone who buys a $400 e-machine desktop package is not the kind of guy to buy a $1800 professional notebook. He left. The PC, after being dropped, never worked again. We never saw or heard from him again.
Even beyond this fantastic story, the PC in the image above, I'd call that about on par normal for some of the crap we had to clean. Sure, most computers just had the sheen of grey/brown dust and caked up fans, but a lot of them, especially those in smokers homes and people with dogs, and for some reason trailer homes just make PCs incredibly dirty. We've actually had to stae in writing to some folks that the attempt to clean the PC might render it useless, and had them sign waivers to protect the store from liability.
I stopped being a manager at that shop in 2002 and moved back to more professional IT work as a network integrator and DR specialist, but the 18 months I spent running a tech bench for a retail shop was eye opening. I can't tell you how many "cup holders" we repaired, how many floppy drives were stuffed full of things by 3 year olds, and how many god awful nasty 4+ year old PCs people wanted to pay os to clean and upgrade (in many cases where an upgrade cost 70% or more of a new PCs cost and still left the old machine FAR below a new machine's specs...)