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What I've read concerning bigger HDs for the MBA is that Toshiba was working on a single-platter (this is the crucial point) PATA 160 GB HD, but that it was not expected to come to market until 2009. Double-platter HDs can obviously hold twice as much information, but their thickness (8 mm) is too much for the MBA, which has space for only a 5 mm thick drive.
 
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