need separate instances/profiles WITHOUT manual profile selection

My wife has a laptop (WinXp, updated) running Firefox 3.6.12 which we both use when away from home. She has more than a dozen saved tabs which of course reappear each time FF is started (and heaven help me if I were to close FF without them being saved!). If a second instance is started, it shows just the home page - great. I'm not game to close the first instance and then the second, in case the saved tabs from i1 get buried (see above para). By way of example, I have Eudora as a mail client on my desktop machine with two separate non-interacting instances. That's the sort of thing I'd like to achieve on her laptop with FF - a separate FF config/icon so that a completely unrelated instance can be set up and saved with its own data - not a dozen+ tabs, but not interfering with the SWMBO setup. Is this possible, and if so can someone tell me how to do it? I should mention that the FF Profile Manager doesn't *quite* do what we would like - ideally two separate desktop icons, each linked to its own profile, with the equivalent of the "don't ask" selected for each so we don't need to manually select a profile at startup. It is possible that both instances will be concurrent.