how do you cut a fallen,hung up tree the proper way with a chainsaw to prevent binding the bar or chain?
any links with photos are appreciated,need to cut a tree that has fallen over a driveway and is hung up against another tree,the tree is still partially connected to the truck,if it didnt hit the tree on the other side of the driveway it would have completly fell.thanks for your help everyone
thank you for all your answers they are all good

Try this site:
http://www.gov.mb.ca/labour/safety/treefelling.html
Once there, search down the page to "Part 2 – Felling Problem Trees", Section 1. iii. Heavy Leaners. Diagrams to show you step-by-step.
Hope this helps and be careful!!
I might be tempted to call a proffessional however I also know what we would do.
Assuming you can get at it – start at the end of the fallen branch and gradually cut small bits off, working your way back to where it is hung up. This takes a lot of weight off the branch, preventing that binding reaction.
Hopefully by the time you get to where it is hung up, you will then be able to wrestle it off the supporting tree -
don’t forget to yell TIIIIMMMBBBER!!!!
Begin cutting down through the limb as you cut the limb will move but stop before it binds the chain. Then under that cut bring your saw up the other side and it should cut through. You may need to continue this to keep it from binding but it will work
Whatever you do, go slow and take no chances. If it weren’t across the driveway, I’d say walk away and wait for the wind to take it down. They don’t call these "widowmakers" for nothing!