Wenco windows have been discontinued, but were made by Jeld-Wen. This is the number that I was given to contact. The insulated glass units are lifetime warranted to the original purchaser. The rest of the window only had a 1 year warranty.
I called the number, and they gave me the closest Jeld-Wen factory phone number so I could order replacement insulated glass units. They are also sending me information on how to remove the balance and sash.
Unfortunately other replacement parts are unavailable. The plastic tabs that go on the bottom of the sash and connect to the springs in the jamb liner have broken off. Without these the windows are hard to open and will not stay open.
I am still looking for replacements for these.
Also, some of the screws at the top of the windows, which are used to attach the springs to the frame, have pulled out.
I have had no problems with the wood rotting, as others have, but I live in a dry climate.