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VeryPC GreenPC Review
The GreenPC succeeds in cutting power consumption by a significant margin and comes with one of the best software and support packages I've come across, so it's very close to being recommended. However, when running Windows Vista, it simply doesn't have enough RAM and performance suffers because of it. So, I'd either recommend getting more RAM or downgrading to Windows XP to maintain satisfactory performance.
VeryPC GreenPC Review