The belt which I can see when I open the car bonnet seems to be new, but my friend says that is not the timing belt and it can not be seen from outside. The car is a Honda accord 2003 V6 which I am planning to buy, with 99K miles. The dealer says he has no idea if the belt was replaced. Is there any way to check if the timing belt has been replaced?
Here is a picture of what I believe your engine should look like:
The red arrow should be what you are seeing. This is the serpentine belt which drives the accessories. The green arrow is the cover which inside is where the timing belt lies. There is no real way to tell if the timing belt has been changed. After a couple hundred miles of running on the engine, it no longer looks fresh, so you couldn't really even tell by pulling the cover. As I'm sure you've been told, in most cars the timing belt should be changed at 60k miles.
With any engine you are unsure of which does not have a complete maintenance history, changing out the timing belt is the first thing I'd do. If you don't and it breaks because it hasn't been changed on time, you'll then have a very expensive paper weight (in most cases). If you are buying 99k mile car without the maintenance history, change the timing belt right off. Better to be safe then sorry.