I'm currently waiting for the ubuntu 11.10 to start using Ubuntu again in dual boot. I have Windows 7 x64 on the HDD now and I'm thinking about buying another HDD for Ubuntu, just in case.
Would it work like this:
I plug in the second HDD and set it to be the booting device from BIOS. Then I start to install Ubuntu on that drive and have the GRUB install on that drive also (it should go there automatically as it's the main HDD?). Then if something goes wrong at any time, I can just make the windows HDD the primary boot device again and wipe the Ubuntu HDD clean? This way I wouldn't have to worry about the windows MBR at any time.
I already have my windows drive in two partitions, one for files and one for programs and the OS. It's 1TB so there would be no problem with space but I would like to be careful as I intend to play around a bit with Ubuntu And a good & fast 320GB HDD is only 40 euros so it's not a big deal..