new motherboard bad drive letter assignment

Hello, I'm new to this forum but could really use some help,

I've just bought and installed a replacement motherboard
specifically Gigabyte EP31-DSL.

I originally tried to install with 3 hard drives and a DVD drive and doing this the system disk was assigned to letter F:

I've since installed a minimum configuration, including my Windows Vista o) system
disk (connected to SATA port 0 on the motherboard).

Unfortunately, when I try to start the system, the system disk is being assigned letter D:
and windows complains there is a problem and tries to repair but no joy.

I've tried taking the CMOS battery out and shorting the CLR_CMOS jumper
but when I restart, the drive is still assigned to D:

Can anyone suggest how I can set the disk assignment back to C:


Thanks in advance