Main reason for computer freezing?

[DKim81]

My dad's computer has been freezing randomly as he browses the internet. The harddrive I know is really old... how would you trouble shoot first?

I am thinking of putting in a new harddrive and re-formatting.

 

[DKim81]

I guess what is the most common cause ?

 

[cubby1223]

My quick list of most common causes:

1) malware
2) spyware
3) memory
4) adware
5) old drivers
6) motherboard

 

[YoshiSato]

Bad Software
Heat
Bad Memory