Thanks for your suggestion, 13thmonkey:
I've now downloaded Windows Live Mail for emails (after doing a bit of research online, it was a toss-up between WLM and Thunderbird, so fingers crossed I've made the right choice. Wish there was something more like Mac.Mail for Windows 7, as it suited me well, but nothing like it came up when I googled 'recommended email programs for W7').
When I've become more familiar with my new pc, I'll try to follow your suggestion to attach my old mac emails to emails to myself (although I'm not sure what you mean by '...group them by something rational etc...' , or '... use sender and recipient for any key people etc....'. It's probably all 'Janet and John' to you, but to me it's 'War and Peace'.
Still, there's no rush at the moment, so I'll cross that bridge when I come to it, after I've familiarised myself with the rest of W7.
Once again, many thanks for taking the trouble to answer.