Can I Have Windows Vista Installed On A Hardrive And Switch It To Another Computer And Vista Work On It?

Activation
What this feature does
Activation helps reduce software counterfeiting, which helps ensure that Microsoft customers receive the software quality they expect. Once your software is activated, a specific product key becomes associated with the computer (the hardware) on which your software is installed. This association prevents the product key from being used to activate the same copy of the software on multiple computers. Some changes to your computer components or the software might require you to reactivate the software.
Information collected, processed, or transmitted
During activation, product key information is sent to Microsoft, such as:
The Microsoft product code, which is a five-digit code that identifies the Windows 7 product you are activating.
A channel ID or site code, which identifies where you obtained the Windows 7 product. For example, it identifies whether the product was sold at retail, is an evaluation copy, is subject to a volume licensing program, was pre-installed by the computer manufacturer, and so on.
The date of installation.
Information that helps confirm that the product key information has not been altered.
If you license Windows 7 on a subscription basis, information will also be sent about how your subscription works.
Activation also sends to Microsoft a number generated from the computer’s hardware configuration. The number does not represent any personal information or information about the software. It cannot be used to determine the make or model of the computer and it cannot be calculated to determine any additional information about your computer. Along with standard computer information, some additional language settings are collected.
Use of information
Microsoft uses the information to confirm that you have a licensed copy of the software and to confirm whether you are eligible for certain support programs. It is also aggregated for statistical analysis. Microsoft does not use the information to identify you or contact you.
Choice and control
Activation is mandatory and must be completed within a predefined grace period. If you choose not to activate the software, you cannot use it after the grace period expires. If you do not have a valid license for the software, you will not be able to activate it.

Only if the other computer is nearly identical to the one the drive came out of.
Every computer is built a little differently, making each load of windows pretty specific to the model it is installed on. You can take a drive out of, say, a Dell XPS and put it into another Dell XPS of the same model number. But you can’t take that drive and put it into a Gateway and expect it to boot up.

if you new computer hardware same is old computer yes it will work
if not you need to reinstall new windows.

It can be done but with great difficulty