Hardware Issues?

I would like to pick the brains of all on here to see if I can get a really frustrating problem fixed asap.
Everytime I go from page to page on the Net or walk away from the computer for more than a few minutes I have to keep clicking Control-Alt-Delete to get any response from my PC.

 

A little more information would be helpful

You say you have to Ctr+Alt+Del, is this because your PC is unresponsive?

Does it show any software "Not Responding"?

Do you have power and/or screensaver options switch on?

What hardware do you have? (cpu, ram etc)

What Operating System are you using?

What happend just before this started? (installation/removal of hardware/software, virus detection etc)

Do you use Cleaning software such as Ccleaner etc?

Sounds to me like you either have too heavy a load on your hardware (possibly recently cause by Hardware failure) but more likely that you are either bogged down or have some form of Virus/Malware or a conflict somewhere.