I just did a fresh install of XP and I installed Quicktime Alternative and K-lite codec pack basic. First of all the screen flickers when I move the movie window, second is that I cant watch fullscreen! The screen is just grayish and displays nothing. Never had any problem with this before. Ive used Klite codec pack and quicktime alternative in the last years.

Anyone know of this problem?

I'm in the same boat as you hobs. I used K-Lite codec pack (standard) for a long while. I seemed to fix the fullscreen issue in Media PLayer Classic by switching the DirectShow output to default (change it by going to:Options, Playback,Output, Default) try playin around w/ the other choices if that doesn't work. hope this helps