I'm sorry but AriehS's your answer is not entirely correct, there are important caveats.
Yes, it is possible and likely if:
* You visit a site on WINDOWS that takes advantage of a browser vulnerability to install malware (but he said he only runs Access, well, yeah, but many people don't consider using the browser occasionally to matter anything at all, besides knowledge is power) .
* You copy an infected file from OS X to Windows, since the malware doesn't work on OS X it will go unnoticed (imagine you receive an infected email attachment on OS X and then drag it to Windows). Of course this assumes you are also not running an AV on the Mac (most modern OS X AVs also detect Windows malware).
AdamB1: Just because someone on the internet of whom you know nothing about says something is safe you shouldn't assume that's a correct answer (don't take it personally AriehS, I'm speaking in general terms).
Last edited: Sep 28, 2013