Dual processor not accepted on w2008 enterprise setup.

I'm trying to install the trial version of W2008 Entreprise X64 on a dual quad-core xeon(IBM x3650-7979), and i've got a blue screen after the file loading, telling me that the installation can't continue due to "dual_processor_not_supported". I used 2 DVDs and got the same problem. 
Any idea?

Thanks.

**The real message actually is:

"A problem has been detected and windows has been shut down to prevent damage to tour computer
MULTIPROCESSOR_CONFIGURATION_NOT_SUPPORTED
...
...

Technical information:
***STOP: 0x0000003E(0x0000000020593FFE,0x0000000020193FFE,0x0000000000000000,0x0000000000000000)"