I'm using a retail version of photoshop 7.0.1.
There was no activation for Photoshop 7.x so there'll be no deactivation option in the Help menu.
Activation was introduced in Photoshop CS (from memory), the version after 7.0.1 (that's CS1, the original Creative Suite version).
This thread refers to CS6 which is why deactivating is required.