Hi Tamar,
You will need to do two things to display the stimulus for 2000 ms even if a key is pressed:
1) Put the word full at the end of any keypresses you define in cells of the time column for your trials where you want the stimulus to appear for 2000ms (See timdrichie's reply for an example)
2) In the style file you will use for this input file write the value of xxx-2000 (where xxx is the minimum amount of time in ms you want the stimulus to appear on screen) in the MinMax column of whatever styles you are using with that input file.
You can find instructions how to do this in the interactive instructions by going to Style Editor > MinMax - Setting RT Limits.
Cheers.
Psychboiler