How do you map a Mac keyboard to PC layout?

I use the following to swap the alt and command/Windows keys. Paste into a .reg file, then run it to import into your registry.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
"Scancode Map"=hex:00,00,00,00,00,00,00,00,08,00,00,00,37,e0,64,00,5b,e0,38,00,\
  38,00,5b,e0,5c,e0,38,e0,38,e0,5c,e0,47,e0,63,e0,0d,00,59,00,00,00,00,00

The main problems with using an Apple keyboard on a PC are as follows:

• Media & Volume keys are nonfunctional
• Command key where Alt key should be, but acts like Windows key
• Option key where Windows key should be, but acts like Alt key
• Right Control key acts like Right Alt key
• Fn key where Insert key should be (wired keyboard only)
• Clear key where NumLock key should be (wired keyboard only)

You can use scancode mapping to map the F7-F12 scancodes to the Windows media keyboard equivalents, turn F13-F15 into the PrintScreen, Scroll Lock, and Pause keys, and make the Ctrl and Alt keys work properly. After that you hit a wall with scancode mapping.

Instead, install uawks. Its a little program that uses AutoHotKey scripts to map your Mac keyboard keys to the PC equivalents. You can always tweak the scripts to get the exact behavior you want.