84 vette been sitting awhile

I have an 1984 Corvette that as been sitting awhile( over an year and half). I am having some sort of film on theinside windshield and windows. I clean it off with window cleaner, and still seems to appear in matter for hours. Any suggestions on why it is happening and how i can clean it for good. Since it has been sitting for awhile, will is be harmful to run it with gas that has been in it for the last year and half?

Thank you  

I HAVE AN 84 THAT HAS NOT BEEN DRIVEN ANYWHERE MUCH IN ACOUPLE OF YEARS EXCEPT I START IT UP EVERY FEW DAYS AND RUN IT AROUND THE BLOCK ONCE IN AWHILE. YOU SHOULD NEVER LAT A CAR SET FOR LONG PERIODS BECAUSE IT IS BAD FOR ALL MOVING PARTS THAT REQUIRE LUBICATION.
SO DONT BE SURPRISED IF YOY START HAVING TO REPLACE THINGS.
AS FOR THE GAS ISSUE , YOU MIGHT WANT TO GO BUY AN ADDITIVE TO THE GAS TANK, THAT YOU CAN BUY AT ANY AUTO STORE, HAVE SOMEONE AT THE STORE PICK UP THE RIGHT ONE.
IT MIGHT DEPEND ON HOW MUCH GAS THERE WSA IN THE TANK WHEN YOU STOP DRIVING IT.
AS FOR THE WINDOW ISSUE , YOU MIGHT BE GETTING SOMETHING COMING THUR THE DASH VENT FROM THE ENGINE COMPARTMENT. TRY USEING A GLASS WAX CLEANING PRODUCT ON THE WINDOW