XiaoBaiTu,
I first came to US on B-1 visa in 1997 and had overstayed for 170 days ( I filed extension but withdrawed after departure). Then I came back on F-1 visa in 1999 and changed to H-1 visa in Mexico in 2003. I have never been questioned on my first entry.
I will submit I-485 next month. Should I worry about that overstay? Thanks