http://uscis.gov/lpBin/lpext.dll/in...?f=templates&fn=document-frame.htm#slb-oi2451
(a) General. Upon receipt, an application filed in person shall be reviewed to determine whether it has been properly filed (signed by applicant, correct fee submitted, and visa available), whether it is complete, and whether prima facie eligibility has been established. If an applicant is subject to the provisions of section 212(e), the applicant shall not be considered prima facie eligible for adjustment unless a letter or other evidence of approval of the two-year foreign residence requirement is presented. If prima facie eligibility is not established, the application shall be rejected. If prima-facie eligibility is established, the applicant shall be interviewed on the same day, or shall be scheduled for an interview approximately sixty but no more than ninety days later. The applicant shall be furnished notice of the date and of the time of the interview, as well as information regarding the required medical examination (Medical Examination and Immigration Interview, form I-486). An application received by mail accompanied by the proper fee shall be immediately reviewed upon receipt in Examinations. The interview shall be scheduled and the applicant notified in accordance with the above guidelines. An application submitted without fee or without signature should be returned to the applicant by RA&I (AM 2793.24) and shall not be routed to Examinations. (TM 4/86)
When Examinations determines that an application has not been properly filed because a visa is not available and that availability of a visa cannot be achieved by approval of a visa petition or issuance of a labor certification, the application shall not be returned to the applicant; instead, he/she shall be sent an explanatory notice of rejection with such other advice as may be appropriate and shall be informed that a refund of his/her fee is being considered. See paragraphs (b-1) and (c) for action to be taken when approval of a visa petition or issuance of a labor certification would make a visa available. An application which does not establish prima facie eligibility, such as those filed by crewman or transits without visas, shall be denied.