computer switching off

my computer is 2 years old.its a pentium 4 ht,windows XP,Medion tower.
when i'm starting it up it seems to take ages and theres a clicking sound coming from it during startup for about 2 minutes.
another problem is that its started to switch its self off then restart for no reason.
can anyone suggest a solution or is it time for a new one.

cheers Pete

 

Clicking sounds usually indicate a dying hard drive. Backup your critical data NOW!!!!

I will be back later to offer further suggestions, if no one beats me to it, but a dying hard drive is not a reason I would buy a new computer. You can replace them for < $100, usually.

 

If your computer is less than two years old, your hard drive might still be covered by manufacturers warranty - some are covered for 3 years- check with the manufacturer- Seagate are exceptionally good, and with fast replacement- if it's Seagate, or, Maxtor.