P4P800, S-ATA and Windows Shutdown

Hi,

I have an Asus P4P800 (Bios 1019) computer and until recently had the 3
x P-ATA Hard Disks (two on Channel 1) and one set as master on Channel
2 with a CD-ROM drive. I had Channel 1 Master logically set up as 10G
Drive C with the remainder mapped as Drive E while the remaining hard
disks where dynamically joined to give me a single drive D. I was
running Windows 2003 server (with all updates). Everything worked fine.

I recently replaced two of the P-ATA drives with S-ATA. Nothing else
was changed. My new configuration is as follows:

1 x S-ATA as Logical drive C and logical E
1 x S-ATA dynamically joined to 1 x P-ATA (on Channel 1 as Master)
1 x CD-ROM on Channel 2 as slave.

I reinstalled - scratch install -- Windows 2003 (with all updates)
and everything is working fine except (there had to be an except)
Windows Shutdown. When I choose this option Windows goes through the
normal shutting down procedure, I hear the HD's power down and the
monitor goes grey but the machine does not actually switch off.

I am at a loss and would appreciate any help.

Thanks,
acb