Open TS2010. Check what version is showing in the bottom left hand corner. If it's showing 42203, you are patched to the latest. (SP2). If you have either 41615 or 41622 showing, you can download SP2 from here; -
http://forums.auran.com/trainz/showthread.php?t=54039
Make sure you download the correct version,
(eg; ending in either 615 or 622). SP2 can take 1 to 2 hours to install, so be patient.
Cheers, Mac...