IANAL , but:
" Unilateral modifications are not supposed to alter the material or important terms of the original contract. "
http://www.faircontracts.org/contract-provisions/unilateral-...
" Unilateral modifications are not supposed to alter the material or important terms of the original contract. "
http://www.faircontracts.org/contract-provisions/unilateral-...
You have 72 hours (10 business days by mail) to undo your consent to the Windows license changes after clicking "Agree". Did you submit your notice in a timely fashion, or did you let the clock run out?