Becuase of the rental charge and time it would take me, I decided to purchase one. Then, I could re-wash the house whenever I seen fit. It was worth its weight in gold. Plus, I can use it for the cars....
Anyway, windows are not a problem. I've washed them the same time I've done the house with no problem..even up close with 2100psi washer.
I used this product called X10, which can be found at http://www.logfinish.com . It did a wonderful job on my dirty log home when I bought it. Great for any kind of bare wood in need of some heavyduty cleaning. I used a bug-sprayer thing to spray it on.