BIOS Boot Menu on that Asus model is accessed by tapping F8 at bootup. Google is your friend,.
You can always copy your files off the Vista drive onto USB flash stick or DVD, then power down and swap in the Windows 7 HD to import files.
In that case, I would copy your User files (Documents, Pictures, Videos, etc) onto stick/DVD, then from Windows 7 explorer, open each backed up folder, "Select All" from Organize menu, then drag the group to that folder in Explorer bar on left side.
Be aware that the left-hand Explorer tree will begin expanding to open sub-files as you drag the file grouping from it's folder over there. To avoid having this flummox your Drag operation, refuse to let go of the left click until Explorer stops expanding and you have cursor on the exact folder you want to copy to.