I think I've fixed my slow POST problems, thanks very much guys. Carefully reinstalled the RAM modules and it seems to be a lot speeder/stable now. Cheers!

In regards to the ATIKMDAG error I don't get that in any games, but I get it whenever I try to run Windows Dreamscene (a moving background - literally just playing a video). I never used to get it with my old ATI card (X1600) but I get it now each time I try to run it with my new card (2900XT).