T42 with ubuntu 60.06 has a hard disk problem

[paulm308]

I installed Ubuntu 6.06 onto my T42 in the second hard disk connected using ultra slim. It was ok in the beginning, but I found recently if I run the application like firefox, the hard disk makes sudden noise, it's like the hard disk is speeding if I open an application. The computer seems to run slower. I don't know what's wrong with it. It's pretty annoying. You guys have any idea?