While scanning, it just froze at a certain file (a video file), so I deleted the file. Then the next scan it still froze, at the same elapsed time (1 minute 25 seconds). A few more tries and it was the same, froze at 1 minute 25 seconds.
It used to stop responding at vdsdyn.dll, but it did not freeze. Now it freezes every time it reach 1 minute 25 seconds. Is this hardware problem? I am getting tired of this problem...

I have an inkling that it is the overheating problem you are experiencing.
Freeze ups and reboots are all a sign that the cpu is struggling.

Hmm if that is the case, what can I do? Will taking it to a service center help or is my lappie finished?

If there are no obvious signs of the vents being blocked by foreign objects such as dust, then it will have to be opened up. It is possible that the fan itself is not working.
Can you feel any air movement when the lappie is turned on?

Yes the air is flowing through the vent even though I think it's weak. However, just by putting my palm on top of the harddisk area (to the left of the touchpad), I can feel that it's very hot.

I tried to unscrew the bolts to open it up to check on the fan but I could not open it (I'm afraid of breaking the plastic cover).

There were a few occasions of crash/blue screen about half a year ago, but it never happened anymore. Days before the freezing happened, the lights went out twice so that the lappie was switched off without shutting down. Maybe it is also the cause?

Could possibly be more than one hardware fault there. If you are not comfortable with opening it up, I suggest taking it to a knowledgable friend, or a PC shop.
Make sure that you have all the screws out if you attempt it yourself :).