Installing curtain hardware problem

I was in Bend, Oregon last week doing what I am doing here in Vancouver, Wash. this week: installing hardware and hanging curtains. But in both houses, one is my sons and one my daughters, when I pre-drill the hole for the anchor to secure the hardware I hit metal, or at least I think it is metal. about 5 inches above the window frame. So another trip to buy a bucket of anchors and spackle. What do the pro's do??? One house is 5 yrs old and the other 50 but with new metal windows.