Keeping the sample speed while playing it in a different key

How do i do that? When i use the pads, they can play the sample in a different tone but then, depending on the key i play the sample loses it´s speed/lenght. It becomes shorter or longer.

How do i play a sample in a different tone without losing the length?

By multi-sampling. Here's a link to a couple of tutorials from MPC Tutor. The second tutorial has the specific info you're looking for but I'd go ahead and start with the first one. MPC Tutor has an e-book coming out at the end of the month that will probably help you a lot, it's not free but I'm bettin' it'll be worth whatever he's gonna charge.

http://www.mpc-tutor.com/tutorials/multisampling1.php

Thanks man, i´ll look into it!

What you need isn't really multisampling, as this does change the length of the notes. You need to perform a pitchshift - but to do this you need an XL as this has a feature called TIME STRETCH. (or computer software like soundforge)

After changing your note to the correct pitch using the TUNE parameter of the pad (or the TUNE paramter in the PARAMS screen in sample edit (shift and 5), you then need to timestretch the sample back to its original length if it's a loop, the XL time stretch feature has a BPM adjustment built in - this will let you timestretch the sample back to the orginal BPM. If it's not a loop, you'll need a bit or trial and error.

This is covered in detail in Chaqpter 13 of the forthcoming E-book, 'Beatmaking on the MPC2000XL'

^yep

Lampdog has a link to a useful sample calculator, that should help out

I actually replied to the wrong post, he had posted a similar question pertaining to playing a piano sample mapped out across a keyboard. I think multi-sampling would be the way to go for acheiving the desired sound for a piano sample. Drunkenmasta, you might want to check out Tutor's Piano multi-samples.