I have degree in math major comp science; am going for job including network administration?

The employer has given me an interview. i worked for Microsoft Seattle as a software tester, but this job requires also database administration, PC hardware support, backups, software support. I don't have a MCSE, or Oracle. PLUS I have been in australia for a few years and pending spouse visa grant was prohibited from working in australia for three years. I am dying to get back into IT but it has been years and this is one of the first interviews i have had apart from manual process work. any suggestions? I have no idea why they are interviewing me but want to give it my best shot, eg havn't got the qualifications they want but demonstrate some knowledge sufficient to get me in the door.l