Rubbing Alcohol is recommended as a cleaning agent to remove stains on vinyl windows.

To finish the process and to remove the rubbing alcohol, use regular Windex window cleaner.

Chart below shows the compatibility of most chemicals with vinyl

Ratings -- Chemical Effect
A = Excellent.
B = Good -- Minor Effect, slight corrosion or discoloration.
C = Fair -- Moderate Effect, not recommended for continuous use. Softening, loss of strength, swelling may occur.
D = Severe Effect, not recommended for ANY use.
N/A = Information Not Available.