Lets clear up a misconception about Windex, as no one ever bothers to see whats in it.
Use only Windex Original (Although Blue looks to be the same from what I've read), not some of the other Windex products as they may contain ammonia and a variety of other chemicals.
Here is the MDS for Windex Original, looks pretty safe to me and I think you'll find similar properties to some of the expensive cleaners (Mmm, namely Distelled water & Isopropyl) that do not have the contents listed in their MDS, wonder why ?
You don't need tons of Isopropyl as it evaporates the water too fast, which is why it streaks.
The Ethylene is fine if you do some reading about it and uderstand its usage.
Material Safety Data Sheet
according to ANSI Z400.1- 2004 and 29 CFR 1910.1200
WINDEX® ORIGINAL GLASS CLEANER
Version
1. Print Date 04/28/2009
Revision Date 01/16/2009 MSDS Number 350000004274
3. COMPOSITION/INFORMATION ON INGREDIENTS
Chemical Name CAS-No. Weight %
Water 7732-18-5 60.00 - 100.00
Isopropanol 67-63-0 1.00 - 5.00
Ethylene glycol 112-25-4 0.10 - 1.00