I find that the easiest and quickest way to convert "numbers stored as text" into numeric numbers is
- Select any blank cell
- Copy that cell (Ctrl+C)
- Select the range which contains the data you want to convert (it's OK if the range includes nonnumeric data as well)
- Use "Paste Special" with operation "add" (I guess "subtract" would work too)
Besides being quick, this has the advantage of converting in-place.
Oh, "Paste Special" is in the Edit menu of "classic" versions of Excel (like Excel 2000). I don't know if it was moved for Excel 2007 and later.