I had the same trouble with 7.10 Desktop Edition. Basically, it seems that the partition editor that runs while installing can't format a drive larger than 50 Gb or so. In any case, the solution is to ...
Long story short - I've got my Mum's old iMac which is a Core i5 2500S vintage machine. 12GB RAM, 1TB spinning drive. Still quite a nice unit, screen is still good, so trying to see if we can make use ...