I've been using Macintosh computers for 24 years and never got a virus or trojan or spyware installed on any of my macs.
As far as a zip file goes, when you click on it, it unzips on your desktop. So as for the unzipped file to begin startup, you have to click on it on your desktop.
This zipped file was 99% not the problem.
As far as checking your hard drive, you should have smart reporter installed on every mac you have. Smart reporter is a free program and will tell you when your hard drive is getting ready to crash, giving you ample time to backup everything.
You usually have at least a week to backup your entire volume before the hard drive goes out.
As far as a mac catching a virus, now you got me laughing.
http://images.apple.com/getamac/images/viruses_header20060428.gif
By the end of 2005, there were 114,000 known viruses for PCs. In March 2006 alone, 850 new threats were detected against Windows. Zero for Mac. While no computer connected to the Internet will ever be 100% immune from attack, Mac OS X has helped the Mac keep its clean bill of health with a superior UNIX foundation and security features that go above and beyond the norm for PCs. When you get a Mac, only your enthusiasm is contagious.
Connecting a PC to the Internet using factory settings is like leaving your front door wide open with your valuables out on the coffee table. A Mac, on the other hand, shuts and locks the door, hides the key, and stores your valuables in a safe with a combination known only to you. You have to buy, configure, and maintain such basic protection on a PC.
On a Windows PC, software (both good and evil) can change the system without your even knowing about it. In order for software to significantly modify Mac OS X, you have to type in your password. Youre the decider. You approve changes to your system.
People attempting to break into computers may disguise a malicious program as a picture, movie, or other seemingly harmless file. You might download such files from the web or get them via mail or chat. A PC just blindly downloads them without a peep. A Mac, however, will let you know that you may be getting a wolf in sheeps clothing. The Mac web browser, Safari, can tell the difference between a file and a program, and alerts you whenever youre downloading the latter.
A Mac gets much of this out-of-the-box protection from its open source UNIX heritage. The most critical components of Mac OS X are open for review by a worldwide community of security experts. Their input helps Apple continually make Mac OS X ever more secure. And its simple to update a Mac with the latest advances. By default, a Mac checks for updates weekly. For pure peace of mind, you can set a Mac to download security updates automatically. Apple digitally signs the updates, so you can be sure they come from a trusted source.
To get a sense of just how big the virus problem is, search for virus at both Apple and Microsoft. Compare the number of results. Whats more, the 100 most virulent attacks cause 99.9% of damage from malicious software. None of these attacks work on Mac OS X. Dont you deserve such protection?
--Mac Lover