Go to:

http://support.amd.com/US/Pages/AMDSupportHub.aspx

Plug all your info in (Desktop graphics, radeon series you have, they type of card you have and OS 32/64bit) and it will spit you out the most recent catalyst software suit.

Edit:
this would be your here (Windows XP, and a HD 5450) I'm guessing you have a 32bit os:
http://sites.amd.com/us/game/downloa...eon_xp-32.aspx

If you have a 64bit
http://sites.amd.com/us/game/downloa...eon_xp-64.aspx

But again if you don't get the results your looking for try other versions. Ultimately I think you will have to play just about the lowest settings with your card. Your card can run the game, but to be honest it will look worst then XI lol. I came from a mighty mighty hd4550 lol, and it was crap, utter crap, but it ran the game. Got to about rank 30, then I could not take it anymore.