Computer not power on

[bigguyone]

Hi Have a Hp dz6609wm had XP OS was haveing prob with some things working right on it, then it started not wanting to turn on. The only way i could get it to come on was dong a hard start. I found out it came with Vista OS so got disk from HP. Now averything works ....But still wont come on unless i hard start it.

Please Help
Thanks