win7 64bit new installation error 0x80300024

I'm running:
VISTA ULTIMATE
Seagate 250GB - VISTA 32bit installed
Seagate 1TB - Data Files
Seagate 250GB - want to install WIN7 64bit
During installation when selecting the blank hard-drive Seagate 250GB for installation WIN7 64bit, I get the following:
ERROR: 0X80300024
and can't proceed.
Any suggestions?

the drive is set as "system drive" not "logical"
platform is definately capable of 64bit
I downloaded .iso from Microsoft Website and used Microsoft suggested free software to create DVD
problem now is: ""unable to create new system partition or locate existing system partition"
any idea?
Helmut