Besides quirks like viruses, spyware, and the Start menu, there are some substantial things on a PC that you lose when you switch to the Mac:
Programs . As mentioned above, there are certain programs that are stubbornly Windows-only. You can always search for replacementsusing Chapter 7 of this book as a guide, for examplebut you may end up having to pay for them. And, of course, there are certain programslike some proprietary accounting and laboratory softwarewhere the Windows versions are simply irreplaceable. For those, you have to keep a PC around, use the Virtual PC emulation program (Section 7.59), or restart your Intel-based Mac in Windows (Section 3.3).
Peripherals . Most add-on devices nowadays work equally well on both Windows PCs and Macs. That includes printers, scanners , digital cameras (still- and video-varieties), and " multifunction " devices that incorporate several of those attributes into one machine.
Unfortunately, not every company is that enlightened. If you have a device made by an obscure manufacturerespecially if the device is more than a few years oldit may not work with your Mac at all. That's especially true if the peripheral uses an old kind of connection (like SCSI) that isn't included on modern Macs.
Still, all hope is not lost. Chapter 8 can get you out of any hardware ruts you may find yourself in while making the Big Switch.