Can I move drive with Win7 easily to backup computer w/o activation?

You cannot avoid activation. If you want to avoid it, then switch to a Linux Distribution. Otherwise, you would be better off with a volume licensing and a KMS server setup to distribute keys to new PCs (you need a minimum of 50 pcs to use KMS) otherwise stick to a MAK (Multiple Activation Key) instead.

More info at: Microsoft Volume Licensing - Product Activation

Ok, scratch the idea of avoiding activation.

Let's say they each server will have it's own license key. The user will have to change the license key and re-activate over the phone upon switching to the backup computer. Is this scenario possible, where the hard drive is removed from computer1 and moved over to computer2 when the first computers motherboard dies, say? How would the user change the key? Would this work with Win7 OEM? Retail? As far as volume licensing, I am now under the impression that this only applies for computers managed in one facility. In my case we are sending 2 computers out to various customers.

Is the hardware is similar such as same motherboard, same sound, graphics then re-activation will be automatic, but if three or more bits of hardware are different, then you will have to re-activate if the auto-process fails. It is very easy to enter a new key using the System Control Panel and select 'Change Product Key', this applies to OEMs as well. Usually each OEM computer with have its own key on sticker attached to the case.
Yes, volume licensing only applies to computers within the same organization or facility.

Yes we use the exact same hardware components. With XP this used to work transparently but with Win7 it is kicking us into 3-day activation period. I was hoping to avoid the hassle of re-activation, but this might work fine..just entering in the new license key and re-activating. Thanks.

Another idea - pre-activate both systems and back up the registration info with something like Advanced Tokens MAnager (or is there a better option?).

When user needs to switch to backup computer, move drive over, and after being prompted to activate, restore saved activation from that backup computer using ATM.

Something like that will probably work.

It does mean a bit more work before sending them out I suppose.

Overall goal is to make it as easy as possible for the user to move the current drive to a backup computer should the primary fail. The windows activation issue has been our biggest hurdle. Doing a bit more work up front is ok if it solves that problem. Anyone see any dealbreakers to this plan?

OK these commands will help you
Open command prompt (admin mode)
type this
slmgr.vbs /upk
This command will remove the current license key from your system
now to install a new product key use this command:
slmgr.vbs /ipk <PRODUCT_KEY>
Enter your new product key in place of PRODUCT_KEY

Tested with Advanced Tokens Manager and seems to work well -- have gone back and forth a couple times so far...