Acer are offering a free upgrade to windows 7 for all eligible Acer laptops that have been purchased since June 26th.
The only catch is... it isn't FREE
You have to pay for shipping, which is £12.87 to the UK, But good value, considering it normally retails for £59.
You'll need to enter the serial number on the laptop to verify the transaction, but apart from that, the rest is easy.
Link to list of eligible models: http://www.acer.com/windows7upgrade/eligible.html
also base units mines x3200