It could be your GPU is over-heating or can't accept the strain of attempting to run Oblivion.
I know that it is scary to mess with your computer components but are you certain that your intakes and fans are clean?
If the fan on the Video Card looks clean then leave it alone, but if not, eventually you will need to clean it.
About the Omega drivers, I know the drivers are old. They are the last Omega drivers to support the ATI 9200. Even so they seem to work well with Oblivion and fix many of the issues.
If you don't feel comfortable installing them then don't.
I would use the Omega Drivers still today if it wasn't for their not being compatible with Windows 7.
I don't feel like writing a driver installation guide but here it is very basic.
You can make a Restore point first if you are scared and return if something goes wrong.
1. You uninstall your old drivers in Control Panel/Remove Programs or whatever. Make sure they are ATI Video Drivers
2. Restart and say No to the Automated Wizard that tries to install your video card.
3. Run the Omega Installer and Restart Computer.
I've been here since nearly the beginning and helped many 9200 users get it working, so other forum members may be able to help too but I know that it is most likely one of the following 9200 freezing issues.
1. Video Driver issue (newer doesn't always mean better when you are talking about a card made 6 years ago or is it 7 now?)
2. Card is over heating.
3. Video Codec is screwing with your card.
4. The 9200 can't handle a certain particle shader and it crashes when spells or similar effects occur.
Solutions for above.
1. Omega drivers have always seemed to fix the 9200 issues.
2. You need to figure this out yourself but visually check your system to assure adequate airflow.
3. Use the Codec Reset Utility I posted above.
4. Use the NoParticle shader I posted above and/or Spellstrip Mod
Read this Post of someone who gathered the files together for you.
http://www.oldblivion.com/sm/index.php?topic=6936.msg78964#msg78964