never heard of it, although if i get an email like that, i will delete it, cause i just spent all day redoing my operating systems. literally installed about 8 OS's (including when i reinstalled it cause it didn't come out right the first time, or the second...). if my system gets hosed now, i will seriously rip someone's head off. If it got hosed 6 months from now, well, i'd probably be happy, cause within 6 months i destroy a computer.
my advise though, if you see something with frogs as a subject, DON'T OPEN IT! even if it's from your best friend/father/mother/brother/sister/grandfather/grandmother/aunt/uncle/arch enemy/that annoying kid down the block/etc. the list goes on.
basically, don't open any attachments unless you know exactly what it will contain. heck, if your not sure, email the person back to confirm what's in the attachment. never hurt to be safe.