Computer Freezes alot (Likely hardware problems)

Recently my computer was overheating alot so i had a friend open it up for me and he helped my internal fan which was cloged with dust. However now my computer is constanly freezing on me at random times sometimes its very frequent while at others i get a good long run before it freezes but this happens alot now and even in safe mode so thats why i think its hardware related. Im not sure what the problem is and some advice would be well appreciated
Thanks,
Confused computer Novice