Thanks for your help everyone!
It’s not a particularly “sensitive” machine as when traveling I use it with an external USB hard drive that has an image of everything on my Desktop PC on it (saves hassles with synchronizing the two machines). But it does have access to various e-mail accounts, most of which have “remember passwords” enabled – and unless you know where the passwords are stored it’s not too easy to “undo” this feature.
I would just make the observation that scrubbing the disk on a desktop PC and re-installing the OS might be a feasible idea (bit time-consuming), doing the same thing to a laptop is not always a Good Idea because many laptops have software installed that you need for the proper operation of the laptop – and it is not easy to reinstall! (Spoken with benefit of experience!)
Once again – thanks for the prompt and useful suggestions