MIDI Problem

This is the problem

- I have WinXP SP 2
- I installed K-lite codec pack
- And even with that i cannot play MIDI files, not with Windows Media player, not with Media player classic nor with winamp
- Curiously I can play them on Quicktime but...
- I don´t want to use Quicktime...

¿Which could be my problem?

MIDI are instrument files, not realy a proper audio file hence why you can't realy play it on a normal music player. You can use Cubase, Reason, Protools (kinda), Quicktime (as you've mentioned) or any other player/music editor that supports Instruments and MIDI format. Give Audacity a go... but i havn't tried it myself yet..

Oh, but I can listen MIDI in Winamp in other computer who also has WinXP....

Sorry for taking a while to respond..
So i assume all other audio types work as per normal then..

try reinstalling your audio codecs:
Device manager open the tree to Sound, video and Games controllers
Remove anything relating to Audio devices/codecs
Reboot the PC and let windows reinstall it.