Fix It Yourself and Save
Time: 30 minutes.
What you need: A ruler or dowel, a pair of window controls ($7, hardwaresource.com), box nails (from $1.50, lowes.com), a hammer, a measuring tape, and a pencil.
Step 1. Push up the window as high as you will want it to open; use a ruler or a dowel to hold it in that position.
Step 2. Place a window control in the channel on one side. Align the top edge of the control with the bottom of the sash; nail it into place. (The wavy part of the control holds the window up and, when pushed in, allows the window to slide over it and close.)
Step 3. Measure the distance between the nails and the sill and mark the same distance for the other channel. Nail the second control into place.
Step 4. Remove the ruler or dowel and lower the window.
A pro charges: $75
DIY cost: $8.50 for supplies