Dreamscene / Deskcapes Problems

[#1]

OK, Vista Ultimate 32bit installed on a 2Gig Turion 64X2 laptop with Radeon Xpress 1100 graphics card.  Graphics card has access to as much RAM as possible (shared setup being a laptop).  Dreamscene available and the Windows sample videos work, however the dreamscene demo doesn't.
Also installed is Stardock's Deskcape software for which some dreams work and others don't. 
Anybody got any ideas why some will play but some will not?  For instance, a 32mb dream will not play, yet a 40mb one will, but then a 7mb dreamscene won't?

[#2]

Do you have the latest vista display drivers for that card? Check the manufacturers website for any updates.

[#3]

Might be worth checking the colour depth and setting to 24 or 32 bit if it isn't already.

[#4]

OK, 32bit graphics selected, latest Catalyst drivers downloaded and installed from AMD and the problem persists 

[#5]

Solved - it was down to my video codecs (so it would appear) - installed CS Codec Solution from this months PC+ magazine and all is now working.