did this and now all I have on start up is a flashing folder with a ?

karen_notkaren wrote:

I did this and now all I have on start up is a flashing folder with a ?

Did what?

If your Mac starts up to a question mark - Apple Support

Hmm, looks like you've erased your Macintosh HD with Disk Utility. If that's the case, we do not recommend doing this.

Otherwise, what else were you doing prior to receiving a flashing question mark folder at startup? Also, it's best to describe your Mac model and year so we can determine the problem further.