You know you can play samples at different pitches by playing on different notes (keys)?
What precisely have you done in the sample editor? Usually this play at the base note speed (using Enter etc) or whatever key you pressed to play it.
Instrument settings might be what you want. Here you can finetune the sample to make it fit more perfectly. Or set it to Sync mode, where you can set how many lines the sample last for.
If you sync a drum sample, then you can put in an empty pattern, select it and use render to sample. Voila, a new drum loop in a different BPM. You can also use render to sample to make crazy drum fx by doing this: