[CentOS] Sound problem in Dell inspiron 1525

After installing CentOS 5.2 on my Dell inspiron 1525 laptop, the sound was inactive, I then installed Alsa-Driver, Alsa-utils, Alsa-plugins and Alsa-libs the ATrpms site. The speakers then work fine, but when I plug in headphones, the sound begins to fade out and eventually becomes completely quiet. I have checked the Volume Manager and nothing is muted including the Headphones volume, when I unplug the headphones the speakers are also quiet. The sound card is a HDA-INTEL. Any suggestions and solutions?

NOTE: THE SPEAKERS WORK FINE, THE PROBLEM ONLY OCCURS THE MOMENT I PLUG IN HEADPHONES. HOW CAN I USE HEADPHONES?