Hello,

My both parents came to visit me to US with tourist visa (B2). They have stayed in the country for total of ~7m (221 days) for 2007.
They do not have any incomes for 2007.
They do not have SSN or ITIN.

Q1: Can I claim them as dependents?
Q2: Can I file as "Head of Household"?
Q3: What do I put in field "Dependent's SSN"?
Q4: Can I live the field "Dependent's SSN" blank? (They are not going to file any tax documents and they will not need ITIN, because they do not have any income)

You should be able to claim them as dependents, but they must apply for ITINs, which means THEy have to sign the W-7s.

Yes, if they file with you, you can claim HoH.

To claim your parents as dependents, it is not required that they live with you or even live in the U.S.
But they must have ITIN or SSN. Can they get the ITIN? I am not sure.

Getting the ITINs should not be too much of a problem, as long as they SIGN the W-7.