1st thing: funny story, I like that Mr. A and Mr. Z. It reminds me of Reservoir Dogs ;)
2nd: It could basically be both, the spybot AND the Emailshit.
As a webmaster (of course ;)) I get every day about 10 fucking Emails saying, read the attached file, watch the picture, read the excel file. Im so sick of it. But as a matter of fact those are all virus infected files. So why don't you go and ask Mr. A (or was it Mr. Z?) and if he's not a jerk he'll tell ya what he's done. And if he won't give him a lesson acording to the price of your new PC
btw. Spyware might only open doors for trojan viruses. That means that another user gets access to your workstation, which doesn't nececcarily mean, that he destroys or deletes something...
anyways...hope I could help you a little...Good luck