You'll have to be able to move the upper sash to get the bead out in one piece, so that is where to start. It is probably painted shut and might have a nail or 2 hiding in there.

Once you do that, you can slide the sash all the way down so that little lip is at the bottom. Run a knife over both edges of the bead and then gently pry it out. If you need to pry it out, use shims or similar on each side of the bead so you don't damage it. Start at the top and work your way down. When you get to the bottom, you should have enough room to twist it past the rail.

If your parting beads are like mine were - ancient, thin, broken, damaged by moisture & abuse & covered with 40 layers of paint - consider breakage inevideble, no matter how careful you are. It was one of the few things I opted to replace but I didn't have much more than random splinters to start with.

UPDATE: on the opposite (right) side, there was a bit of a gap between the upper sash meeting rail and the parting bead, and I was able to get that one out unbroken. Thought I was home free. Alas, the window still won't come out. I need to get it to drop about 1/4 inch. I'm going for the heat gun and scraper now.

For years I have simply destroyed them to prevent and other damage during removal and made and installed new ones.

I still have a handful of them stored in the basement ceiling between the joists.
It is easier to make a batch with one saw setup and use them up then make them a few at a time.

Have you tried scoring the paint between the upper sash and casing on both sides? Alternatively, how about clamping the sash rail weatherstripping flat to the window--then it will slide past the middle of the parting bead if the paint is freed.

My attic windows all have the upper sashes fixed, whether by accident or not, and I generally didn't think the effort was worth it there--other rooms, yes. The two largest windows in my house are about 46" wide, the upper sash is diamond paned, the lower, one big sheet about three times the height of the upper: both are fixed in place, but flanked by narrower operable windows. For energy conservation reasons, I don't intend to free up either of those big monsters! :)

Should you break a bead, you can get replacements at a lumberyard.

A window zipper is a invaluable tool for this operation, along with a thin but stiff putty knife, a fishtail trim removal bar, and the always available string of expletives.
Fishtail bar:
http://www.grainger.com/Grainger/ESTWING-Moulding-And-Nail-Puller-2UV16?Pid=search
Casey

Here is a link that might be useful: Window zipper

Sadly the parting bead did not survive the removal. And even after that, the sash didn't want to come out. I finally got it to move and it turns out that the upper sash has a pulley system! It looks like the original cords - there is black soot on the cords and sash edges.

So now in addition to the sash painting project, I want to change out the pulley cords.

"Sadly the parting bead did not survive the removal."

Just view them as sacrificial.

Preventing other damage to the window structure during removal is far more important.

I tend to break about 25% of the parting beads when I removing them from my windows as I restore them. Like the others I recommend having a supply of extra ones on hand because breaking some is going to be inevitable. I did luck out and find a couple of extra parting beads that got stashed in a weight pocket that I found while working on one window. My local lumber yard has them in their molding inventory.

One trick I found in getting those stubborn bastards out is a pair of sheet metal pliers. The wide grip really helps in getting them out without a lot of damage.

Diane

Here is a link that might be useful: Sheet Metal Pliers

"My local lumber yard has them in their molding inventory. "

Thy are easy enough to make on a table saw.

"NOT so easy if you do not have a table saw!"

The go to a real lumberyard and have them make a few.

If you have a portable circular saw you can often rip them from the edges of a board.

If you have a portable circular saw you can often rip them from the edges of a board.

You are a much better carpenter than I. I had the lumber yard do as you said.Me and the tape measure do not see eye to eye when it comes to wood.