Just install Win7 to the other hard drive and it will automatically set you up to choose which ever OS you want. If you want to, you can even go in and set up the boot menu to set Win7 as the default with say a 5 second time out at the menu? That way, if you don't choose, it will boot into Win7 by default.
Here's how.
■Launch an administrator console window to the OS prompt in Windows 7
■View the current default boot setup after installing Windows 7. It's probably already Windows 7. To view the default boot setup, run bcdedit /enum {bootmgr}
■You might see something like this:
[cpp]Windows Boot Manager
--------------------
identifier {bootmgr}
device partition=\Device\HarddiskVolume1
description Windows Boot Manager
locale en-US
inherit {globalsettings}
default {current}
resumeobject {24a500f3-12ea-11db-a536-b7db70c06ac2}
displayorder {current}
toolsdisplayorder {memdiag}
timeout 30[/cpp]
■The default value of {current} in this case would mean whatever OS you allowed it to boot up into. If you are in Windows 7 (without choosing at the menu), then it's already set for Windows 7. If it's Vista, then you need to do the next step.
■To change the default entry if it's NOT Windows 7, then run the following command: bcdedit /enum
■Note which entry is for Windows 7 and note the value of the identifier attribute. You will use that value in the following command to change the default boot entry to Windows 7: bcdedit /default <id>
■Next, change it's boot time-out to 5 seconds: bcdedit /timeout 5
That's it. Now it will boot into Windows 7 within 5 seconds if you don't choose a menu option.
As for copying documents, just use the Easy Windows Transfer program. Go into Vista and run it from the Win7 DVD to get it installed/updated and then run it in Vista to backup your files to a directory/usb stick/DVD.
Then, boot back into Win7 and run it from your start menu and restore all your user account documents/settings/etc.