From IRS site
"Taxpayers must have valid Social Security Numbers to qualify for the stimulus payment. If married filing jointly, both taxpayers must have a valid Social Security Number. And, children must have valid Social Security Numbers to be eligible as qualifying children.
Taxpayers who file their tax returns using an Individual Taxpayer Identification Number issued by the IRS or any number issued by the IRS are ineligible. Also ineligible are individuals who can be claimed as dependents on someone else’s return, or taxpayers who file Form 1040-NR, 1040-PR or 1040-SS."
Also to get rebate check you must file your 2007 tax return. You must have minimum of $3,000 of eligible income (does not include interest, capital gains,..). check this link:
Tax News