I had a dead laptop lying around, and I wanted to upcycle it into something useful in my room. My window also would not stay open, so I hacked them together, allowing my window to be propped open by a laptop.
Step 1: Obtain a laptop
Ask your friends if they have one, break one, find one in Best Buy's dumpster, etc.
This is the single most important step.
Step 2: Jam laptop in window
Place the laptop between the window and window sill, and let the window put its weight onto the laptop, jamming it in place.
Step 3: Enjoy the breeze!
Now feel the refreshing breeze blowing through your open window. Give yourself a pat on the back for upcycling a useless component as well!