All forwarded messages are false. Maybe, but I've never seen one, and I've been getting forwards for years. I'll say it again, in great big letters, for those who weren't paying attention. All forwarded messages are false. Embroider that on something.
Companies never send out virus warnings via forwarded email.
In fact, Microsoft and IBM don't even issue virus warnings. Since most viruses exploit flaws in Microsoft's programs and operating systems, Microsoft would prefer to keep virus talk as quiet as possible to keep negative attention away from the bug-infested atrocities they spew forth. Bill Gates is far too busy to send you email. The Old Navy lady and the president of the Gap are, too. And he's not gonna send you email, either.