Also - If you are using Fruity Loops. You can click on the sample and bring up the channel settings. Under time stretching you can click resample and then put "tonal". But be sure to correctly time strech. If you are a beginner then i suggest you try to cut your chops in the presets for the timestretch knob. This is right next to the "resample" tab, to the left. If you right click on the knob that says "time" on it you get a couple of options. I'd advise to try to keep chops to these simple preset times (as in count off beats, just to get yourself in the rhythm) 1 beat, 2 beats, 1 bar, 2 bars, 3 bars, 4 bars. Just 'til you get the hang of it. Not sure what you are using, but let me know if its not FL.
EDIT: Not sure if you are talking about samples from one song, or samples from multiple tracks btw.