Sorry for the delay. When you deal with a lot of threads, it's very easy to forget about one.
Are you still having issues with this?
I have reviewed your logs that you uploaded and it seems that the culprit file is this:
(12:07:14) Loading C:\Users\WindWalker\Desktop\Dirt 3 Extracted\xliveinstall.dll
(12:07:58) Exit code: 0x800b0100
Can you zip it up and attach it to your next post please?
C:\Users\WindWalker\Desktop\Dirt 3 Extracted\xliveinstall.dll
I am really sorry I lost this thread, Secilu.
If xliveinstall.dll is not damaged, then media2.cab is:
(12:07:58) Verifying C:\Users\WindWalker\Desktop\Dirt 3 Extracted\Media2.cab failed [Code:0x80073602]
(12:07:58) File 'C:\Users\WindWalker\Desktop\Dirt 3 Extracted\Media2.cab' was not signed correctly or its contents are invalid.
(12:07:58) Verified files [Code:0x800b0100]
Looks to be a damaged, dirty, or scratched disk.
Your only option is to try to clean it, but there is no guarantee it won't make the problem worse - but then again, it isn't working now either.
Use a soft, non-abrasive cloth, which doesn't leave fibres, to rub the disk. Work from the inside out, gently but firmly wiping away any dirt. Do not run outside to in, and certainly never ever rub around in circles.
If you need any more help, please don't hesitate to ask. Are there any obvious really deep scratches? These require a bit more work to deal with, and are much, much less likely to end well.