Just type a normal x, then highlight and press the sigma button.
Kind of looks like a backward E and its beside the YouTube button.
::EDIT:: Oh, in MS Word? I have no idea.
you could use insert>special character on word
I found these also, press alt and the number
Alt 241 ± Plus or Minus
Alt 47 / Fraction seperator
Alt 0188 ¼ Quarter
Alt 0189 ½ Half
Alt 0190 ¾ Three quarters
Alt 46 . Decimal Point
Alt 240 ≡ Exactly Identical
Alt 61 = Equals
Alt 247 ≈ Approximately equal
Alt 60 < Less Than
Alt 62 > Greater Than
Alt 242 ≥ Greater than or equal
Alt 243 ≤ Less than or equal
Alt 251 √ Square Root
Alt 252 ⁿ Power n
Alt 0185 ¹ To the power of 1
Alt 0178 ² squared
Alt 0179 ³ cubed
Alt 227 π Pi
Alt 248 ° Degree sign
Alt 35 # Number
Alt 236 ∞ Infinity
Alt 230 µ Micro
Alt 228 Σ Sum
Alt 239 ∩ Suggest definition
Alt 244 ⌠ Top half
Alt 245 ⌡ Bottom Half
they might be useful [although there is not an there.