help with installing update 2

When I ran the installer for Storyline update 2, I got the message "The following error occurred on C:\Program Files\ Articulate\Articulate Storyline\Player.dll  Access is denied (0x5)" even though I'm the administrator on my computer.  I was thinking maybe I'll have to uninstall the previous version first, but I'm not sure whether I need to find some sort of activation code or something ahead of time so when I install the new one it'll know I'm a registered customer.  Could someone offer any suggestions?  I'm eager to try the new update to see if it fixes the low memory messages on my XP system.

Thanks!

Dorothy