OEM gives no direct support from Microsoft, BUT you can still call to get
activation..
This passage is extracted from a web site.. the link is at the bottom of
this post
How do I activate Windows?
You can activate either online or by phone. To activate online you need an
Internet connection. Activating by phone requires interacting with an
automated phone system.
To activate Windows on this computer, do the following:
Open Windows Activation by clicking the Start button , clicking Computer,
clicking Properties, and then clicking Click here to activate Windows now.‌
If you are prompted for an administrator password or confirmation, type the
password or provide confirmation.
You can then select the method you want to use to activate.
Note If you chose to automatically activate Windows online when you set up
your computer, automatic activation begins trying to activate your copy of
Windows three days after you log on for the first time.
http://www.windows-vista-update.com/Windows_Vista_Activation.html