Get a new chisel scraper, sometimes it may take two scrapers to help ease out the bead. Not all beads come out the same but generally for internally glazed firmly push the scraper into the gap between the bead and frame roughly in the centre of the sash.
Once it's in ease it to one side keeping the scraper blade straight. Keeping the scraper in place move down slightly and ease to one side again ( this is where you may need the second scraper). Keep doing this until the bead comes free then you can put the scraper in the gap you've created and push all the way through, move up and down to free the rest of the bead and remove.
For the rest of the beads start in the corner and repeat the above moves, they should come out easier because they'll have no restriction.
Externally glazed may have a push in gasket on the inside of the window. Remove this by carefully easing out with a blunt scraper, depending on it's age it may rip so caution is advised. Once the gasket is removed push the glass from outside towards the back of the frame and the beads should come out using the method above, there will be less pressure so they'll come out easier.
If they have security tape then use the method for internally glazed but you'll not be able to toe and heel without cutting the tape and replacing it.
Some beads come out sideways, some straight. It depends on the profile. Some easy, some down right impossible. Glazing the same, whichever way they come out that's the way to put them back in.
I think I've covered it all and hopefully it makes sense, good luck.
