Mouse/ Keyboard or System problem?

[Vmm]

Hello Everyone!
I have P4 system. And Windows xp installed.
The problem is, on browsing internet after 2 hours the computer
becomes stop with no mouse movement.
When It hits CTRL+ALT+Delete then it works well... but after few
moments Mouse/keyboard becomes stable and also the whole operating system stops responding...
The only way for me at that time is to hit restart button of the pc. Then again works. and problem repeats after some time..

Please tells me its a software or hardware problem..
I have installed the Windows XP SP2 and SP1 one by one by formating C drive
but the problem exist...

 

[Rik]

It could be heat. Make sure your pc is free of dust and that all fans are working properly.

 

[Vmm]

CPU Temperature = 47c/116f
MB Temperature = 42c/107f

I think the Motherboard is going old and creating problems
as its age is 2 + 1/2 years.//??

 

[Vmm]

Is there is any solution ot it..
Its not only the mouse or keyboard problem. Its whole
system which stops responding, if I dont use it for 15 minuts/.