Microsoft Word supports extended fonts, with character sets containing more letters and symbols (called 'glyphs' by typographers) than are used in English. By using the Windows Character Mapping utility, you can even add custom symbols to existing fonts, which will be accessible by all programs. The Ribbon interface of Microsoft Word 2007 and Microsoft Word 2010 puts some symbols into a flyout palette for quick selection.
Click on the "Insert" tab.
Click on the "Symbol" item. It has a picture of the Greek letter "Omega" and is on the right hand side of the ribbon bar. A palette will pop out.
Click on "More Symbols." A floating dialogue box will pop out. Select the symbol you want to use; if you do not see the symbol you want to use, use the drop down menu at the top of the dialogue box and change the font.
Click on the symbol you want to use, then click "Insert." It will show up in the "Recently used symbols:" list. Click "Cancel" when you're done, and close the dialogue box.
Click on the "Symbol" icon on the ribbon; you'll see the symbol you selected on the palette on the dialogue box. The palette shows the 16 most recently used symbols chosen.
Click on the "Start" menu and select "Run." In the dialogue box that comes up, type (or cut and paste) the following:
This will launch the Private Character Editor.
Click on any of the grey boxes in the launch window. You may also want to select a specific font; by default, the custom symbol you make will appear in all fonts.
A 50 by 50 square grid will come up with tools similar to those for Microsoft Paint. Draw your symbol out by turning squares from white to black, like you're laying mosaic tile. You can also copy and paste between the Character Editor and other bitmap programs, including grabbing a character that you want to modify; this is faster than making a character from scratch.
Save your character by going to the Edit menu and selecting "Save."
Associate your character with a specific font by going to the "File" menu and selecting Font Links. You'll be given a dialogue choice -- All Windows Fonts or tying it to a specific font. Either way, the new character will show up in Microsoft Word's Symbols dialogue box as a selectible icon.