Can OEM OSes be transferred from one HDD to another?

I have two scenarios that pertain to the topic in question.

1.) If my hard drive fails, can I use a WinXP disk and my installion key (that I’ve previously made record of) without violating the EULA?

2.) If a working drive is nearing capacity, can I somehow deactivate the first installation of WinXP and install that OS (and Office software) on a bigger hard drive?