How to UNPIVOT to split columns into rows?

I've got a sql query (using MS-SQL 2005) that generates data with these columns:

TimeStamp | SpeedMax | SpeedMin | HeightMax | HeightMin
-------------------------------------------------------
10        | 50       | 10       | 300       | 70

The form I need it in though is this:

TimeStamp | Speed | Height
---------------------------
10        | 50    | 300          <-- one row for the max values 
10        | 10    | 70           <-- a second row for the min values

Given the first result set... what query would I need to get the data into the second format? I think it might involve an unpivot, but I'm new to that, and am having trouble working out what to write.

Thank you very much.

From stackoverflow

• SELECT TimeStamp,
         minmax,
         CASE WHEN minmax = 0 THEN SpeedMax ELSE SpeedMin END AS Speed
         CASE WHEN minmax = 0 THEN HeightMax ELSE HeightMin END AS Height
  FROM Table,
  (
      SELECT 0 AS minmax
      UNION ALL
      SELECT 1
  ) mm
  

  You may add

  OPTION (FORCE ORDER)
  

  to avoid double scan on Table

• Try

  SELECT TimeStamp, SpeedMax AS Speed, HeightMax AS Height
  FROM Table
  UNION ALL
  SELECT TimeStamp, SpeedMin AS Speed, HeightMin AS Height
  FROM Table