They may not have a leg to stand on...
... Unfortunantly, when you go looking for win7 eula from Microsoft, available at :
Then, when you make the choice of:
home basic (or any based on multiple random checks)
then wait for the pdf to load, it seems that the eula shows:
"By using the software, you accept these terms. If you do not accept them, do not use the software. Instead, contact the manufacturer or installer to determine its return policy. You must comply with that policy, which might limit your rights or require you to return the entire system on which the software is installed."
So unless it has changed since this started, its up to the manufacturer/installer to decide if they will give a refund or not.
It does not say "If you do not accept them, do not use the software. Instead, return it to the retailer for a refund or credit."
This appears to only apply if you purchase as "packaged" software (buy the software separately in its own box it may appear) or from Microsoft directly.