Afraid I can't help you with the window. But the floor--if the sound you are hearing is not the upstairs person's footsteps but the actual floorboards creaking, there are some remedies. Unfortunately, most of them are things that I consider in the landlord's perview, not a tenant's. Most involve screwing into the floor to stop the creaking by more firmly attaching the floorboards to the joists. It can get expensive. And not all landlords will be willing to take that extra step to stop the noise. And it's not something that you can do from your apartment.

Even if the upstairs person adds areas rugs to her floors, it won't help the creaking very much. I know, I was that upstairs person in my last apartment. It took me months to convince a new landlord that I wasn't stomping around in army boots all the time; I was walking around barefoot and had covered 80% of the floor in area rugs. But the floors in that 180 year old building creaked. I was sorry to bother the downstairs neighbors, but some of the floorboards creaked when my cats walked on them. The landlord looked into fixing the problem but decided that it wasn't worth the money.