Final answer:
To see conversion rates for Windows visits from London, select 'Operating System' as the primary dimension and 'City' as a secondary dimension, then view the Goal Conversion Rate.
Step-by-step explanation:
To view the conversion rates for Windows visits coming from London, you would need to set your primary dimension as 'Operating System' to segment by Windows users. Then, you should add 'City' as a secondary dimension to further segment by location, specifically London. Once you have these dimensions set, you can view the corresponding Goal Conversion Rate for this specific segment of users.