I know this must be simple, but I just can't find where --- when I import samples into X3 from the Media browser, or from my hard drive, is there a setting which makes them automatically convert to the BPM of the track, or, if I prefer it not to do that and just have the sample play exactly as it is regardless of time?    Currently I'm importing some samples and they are playing back slower (and at different pitches) than expected ...

drag and drop from the browser or from windows explorer.
they are not in time with your BPM because they are not asidized/groove clips.
right click on the clip and choose "Groove clip looping" from the drop down list.

Thanks for the reply - actually I didn't want them in time, I just wanted the sample to sound exactly as it is without any change from the original. I found out that in the Loop Construction view, the "loop" button is on, and I can turn the loop function off  by choosing "Clip"  -  "Loop On/Off".