Can I use an external HDD for Boot Camp?

You can not run Windows from an external drive.

That is the opposite of what I said, so here, a little louder NO

As far as I know BootCamp doesn't currently support using an external drive as your boot device for windows. However, as long as you install windows to a portion of your internal drive, there's nothing stopping you from installing apps and games to an external hard drive. You just need a large enough partition on your internal hard drive to install Windows.

They say 16GB is the minimum for 32bit windows 7 and 20GB for 64bit. You'll probably want to give it a bit more breathing room for the bootcamp drivers which take up a gig or 2, and also Direct X, and other things that games need.

When you install a game, you are almost always presented with the option of choosing a custom install, which allows you to specify the folder the game is installed to. At this point, if your external drive is connected and formatted as NTFS, you can create a Games folder on it, and choose to install your game there. That should do it.

20GB is the actual size of the Windows OS, that does not allow or account for:

page

hibernate

cache and temp/tmp folders that are needed

creation and setup of default user

applications and drivers that you can't or would not want on 2nd NTFS volume

10GB for update space like SP1 and above

free space for any OS to function properly and have 20% free overhead (same for OS X though I would insure more like 30%)

page and hibernation can be very useful and you can't actually totally disable page file if Windows decides it needs some.

40GB minimum and 50-60GB to be on safe side. Too little too small and you would find you can't log backin after a restart and updates

I'm not sure your numbers are quite right. I have Windows 7 Home Premium 32bit installed right now with Service Pack 1 on my bootcamp partition. I've also got Steam and Deus Ex: Human Revolution installed. Steam and the game occupy 8.47GB of space. Total space occupied on the disk is 21.2 GB, which means Windows is taking 12.73 GB. So I'd say the system requirements of 16GB for 32bit and 20GB for 64bit definitely include cache and paging, and also account for service packs and drivers.

You could easily get by with 20GB minimum space for a 32bit install on bootcamp, if you're installing all apps to an external drive.

FaceLord wrote:

I'm not sure you're numbers are quite right. I have Windows 7 Home Premium 32bit installed right now with Service Pack 1 on my bootcamp partition. I've also got Steam and Deus Ex: Human Revolution installed. Steam and the game occupy 8.47GB of space. Total space occupied on the disk is 21.2 GB, which means Windows is taking 12.73 GB. So I'd say the system requirements of 16GB for 32bit and 20GB for 64bit definitely include cache and paging, and also account for service packs and drivers.

You could easily get by with 20GB minimum space for bootcamp.

Take a moment and read the posts on this site, users who installed Windows in a 30G or less partition come here regularly trying to find the easy way to make it larger. We'll help you when you need the space. 🙂

Windows 7 should not be installed in less than a 40G partition, larger if the drive is an SSD.