If you still haven’t downloaded the public beta of Windows 7, you’ll need to do so before February 10th, as Microsoft will be pulling the links from its servers.
If you’ve got a slower connection and you start your download by the 10th, you’ll have until the 12th to finish downloading the multi-gigabyte file. The good news is that Microsoft will continue to make product keys available for the beta long after the 12th. So if you can find the ISO elsewhere – and there should be plenty of places to find it – then there’s no need to panic.
General availability for the Windows 7 Beta to end [Windows 7 Team Blog]