Lpc2000

> 
> Is this some typing error ???
> Should be:
> 
> IO0CLR = LED;
> 

Yes, it is.

> Also try adding a default ISR or write this:
> 
> VICDefVectAddr = (unsigned long)timer0ISR;
> 
> And see what happens.

I added this line, I also tried adding:
VICVectAddr = (unsigned long)timer0ISR;
But it didn't work also.
Best Regards
Peter