I had exactly the same problem (I think).
In my case the CD was reading as if my cd drive was 1.5x drive.
Here is a very slow temporary solution that should work: Copy the files from both discs to a directory on your computer and install from there. (For me the copy took about 60 minutes (and sounded like my drive was getting trashed) but it worked eventually (don't autorun - do the shift thingy or disable autorun).
Ive found the problem now affects other disks with very large install files (starcraft has a 650meg install.exe and BDiv has a 700meg setup.exe) - but it's the first time ive ever had a problem like this and I can't find an answer on google.
Can anyone suggest a more permanent solution - it's diriving me nuts....
(BTW: Most disks work fine - it's just a few - and -no- they are not scratched - they are spotless... <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
