The total installation on the 250GB hard drive (will be) much, much less than 160GB.

I'm about to install Windows 7 to a 250GB 7.2k RPM because of the need to have a machine up and running today. In about a week, I will have to switch out this drive for a 160GB 10k RPM drive.

How can I go about doing the install and then the image and make this is painless as possible?