Mate said his mac is infected. Never used or mac or intend to. So il leave the suggestions on whats good to sort it up to you.
Have never used a Mac however this search has allot of links:
If he is a mac Fanboy tell him "I thought mac's couldn't get viruses " . If he is just your average pc user actually help him
already told him that personally i hate macs,
I posted him your google link, i had already looked at google but there no point me suggesting one as iv never tested it.