Notebook Freezing Problem

Hi There, my old notebook is freezing very often especially when I play videos using media player or play music. Could it be due to HDD problem? I hear sound like scratching on plastic everytime it access files from HDD whichdoes not happen on my new Notebook. When it freeze the hard disk stop rotating ( theres no sound), I need to push power button which promt me to shut down menu with an option of Stand by, Turn off and Restart or Cancel. Then it start working normal again after clicking Cancel.

Specifications are Fujitsu Lifebook , P3, 850mhz, 256 MB SDRAM with Win XP Pro.

It is originally desgined for Win Me. I changed the Oses one year ago. Theres no warranty (expired 4 yrs ago).

And 2nd Question The other notebook is pentium mobile with 1.86 Ghz but it runs only on about 789 MHZ even when I use intensive task like converting videos or DVD etc and took many hours. Will it take shorter had it run on its full processing power? How can I change this to run on it's full power.