No extra details given here than in your post in the Community Poll forum post.
Which media player are you using?
My own research for the HP pavilion XT978 shows that;
1] Processor, Pentium (R) 4, 2.0GHz/400 processor
2] Memory, (RAM), standard 512MB upgradeable to 1.5GB
3] Video Card, GeForce2-MX200 32MB SDR
But I don't know if you have upgraded either RAM or the video card from standard specs. That graphics card seems to have quite low memory, and was originally designed for "Microsoft Windows 2000 ? Microsoft Windows 95 ? Microsoft Windows Millennium Edition". I'm not saying it is incompatible with XP, obviously not, but 32MB is low.
It all matters. Full sized video needs a lot of video graphics memory and this card doesn't have much. If you're attempting to watch a full screen "High Definition" video, then the problems get worse.
Does this happen to all videos you try and watch in full screen mode, or just some? What type of videos, eg DVD films, or clips from the internet, or digital video camera?
Has this ever worked? if so, what has changed since it last worked?
Windows XP is my OS, P C is HP pavilion XT978. My Promblem is when I try to englarge a video, up pop a blank page and when i hit escape it just returns to the small size. help