How to make a system partition, which is needed for Win

Hello everyone,

i have a netbook with 160gb.
Xp is pre installed on this machine.

I made a new partition of 25gb to install Windows 7 on (from a usb-stick).

The installation screen starts up oke, but when i start the install and select the 25gb partition i get the message that it's not a system partition.

So now my question, how do i make it a system partition?

Thnx in advance

Did you format the partition?

Yes i did a quick format and a "slow" format but both didn't help.