Hey Ko-NSX,
I've done some searching for you, but you need to provide more tech details here:
What Operating System are you using?
What drivers are you using, and what version are they?
What version of DirectX do you have installed?
Some potential reasons for your problem:
The Radeon Mobility 7500 is quite old. It's a DirectX7 based video device, and comes in 16MB or 32MB. From what i found, it uses integrated system memory [your RAM]. It has no Shader Support (becoming important in games). I obtained these details from <A HREF="http://www.ati.com/products/comparisons/mobilitycomparison.html">here</A>.
If you check the <A HREF="http://www.unrealtournament.com/ut2004/specs.php">UT2004 system specifications</A>, it requires a Video device with 64MB video memory, and it's a DirectX8.1 game.
The low amount of video memory (which is also sharing your system's RAM) might explain why textures are being lost. I'm not sure how UT2004 runs with such an old card.
COURSE OF ACTION:
You should be able to play a DirectX8.1 game on a directX7 card no problem - it just wont support some graphical features and may be slower. Make sure you have DirectX8.1 or DirectX9 installed.
Also, check the Sony website for the latest ATI video drivers. I'm not looking to start a flame war (seems the IT people are overprotective of their video cards) but no offense, ATI has a bad reputation with their drivers. Make sure you have the latest version.
i really need to go to bed. hope this helps.