I would not use Powerpoint as it is a pretty in flexible tool - you cannot easily highight or draw onto your slides and you cannot change the order of your slides easily. Powerpoint is great if you want slick presentations to large audiences.
For most smaller groups flip-chart, white board or overhead slides work better. Note you can always prepare overhead slides and flip-charts ahead of time if you don't want to draw 'live'
Alternatively use Powerpoint to prepare some slides for overhead projector use. Then you can change the order and annotate live.
Note LCD projectors are very good but still run at about 2000 US or 1000 GBP - great for home cinema use as well!