Dual boot with windows 7

MY OS IS WINDOWS VISTA ULTIMATE, AND IT´S WORKING WELL. BUT I INTERESTED IN LEARN THE NEW WINDOWS 7.
CAN I INSTALL WINDOWS 7 IN DUAL BOOT WITH WINDOWS VISTA?
I HAVE 3 BIG HDs AND MANY SPACE.

I would recommend disconnecting all drives, including the Vista drive and doing a clean installation on the chosen drive.

Yes, you can dual boot Win7 with Vista. You can even do it with an Upgrade, although you are supposed to stop using Vista once the Win7 Upgrade is installed.

Since you want to keep your Vista, I would buy a full retain version of Win7, boot from the installer and install it to another HDD.

If you want Win7 to configure a dual boot menu, leave the Vista drive plugged in along with the Win7 target drive. But unplug all other drives during install.

If you unplug the Vista drive during Win7 install to another drive, you can control which drive it boots to by setting that drive to boot first in BIOS, or using BIOS boot order shortcut key (normally F10).

The drives should still be visible to each other once both are plugged in.