I suspect I could sell 5 ot 6 at work. I think there's a big enough market for an extremely cheap PC. Low-income family with 2 (or more) kids, for example - a PC for each kid instead of one for them to argue over. There are also plenty of people who would like a PC and can't afford (or can't easily afford) the £350 or so for a budget system. There are people who have a games console, a DVD player, etc and just want a PC as pretty much just a word processor and web browser.Can't see there being any market what so ever for a PC that cheap/crap. You'd be making no more than a fiver on each one sold - and you won't sell many.
As for not knowing how to use Linux...we're talking about people who don't know how to use Windows, so the gap isn't that big. Preconfigure everything and they're good to go. If anything goes wrong, they'd be just as lost with Windows as they would be with Linux.
That is...until they buy a PC game (or one of the aforementioned children buys a PC game). They have a PC, right? So the PC game should work on their PC, obviously.
They probably wouldn't be happy with you at that point.
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