I heard that due to the weight of the a/c, the window can be damaged. I'm looking to buy a window a/c that weighs 60-70lbs Please let me know if you had any problems and have any solutions. Thank you!

They make a mount that goes outside just for this. it relieves the window of the weight.

Hope this link works...
http://www.lowes.com/lowes/lkn?action=productDetail&productId=54691-1410-ACB160H&lpage=none

No problem with my Vinyl windows, I used a support kit for the outside , make sure you use one worked great!