Why did Petunia Dursley accept Harry at the beginning?

Fri May 28 03:38:32 UTC 2004

No: HPFGUIDX 99624

Dumbledore explains to Harry at the end of OoTP the magic protecting 
him at Privet Drive-but why did Petunia accept the baby on her 
doorstep, when she and Vernon wanted nothign to do with Lily's 
family? 

On a related note, is Harry vulnerable to attack by Voldemort when he 
wanders around Little Whinging? Dumbledore said that he is protected 
only when he is in the Dursley's house.

"mariofett"