A boot timer will only tell you how long it takes to boot - it wont tell you individual program launch times nor why it's taking that long.
How many startup items do you have? It sounds like Windows is loading a bunch of stuff before finally opening Media Centre. Does Media Centre take an age if you open it yourself after Windows has fully started [i.e. kill any MC process and reopen].
Stop MC from opening with Windows.
Reboot Windows and let it settle down [i.e. everything is loaded]
Start Media Centre
This is important because it should tell you if it is Windows taking a long time to settle down, or if it is MC taking its time.