Unfortunately the Micro$oft geeks decided that the useless POS termed 'Windows Live Mail' would be the so-called replacement for Outlook Express, so OE won't work with Windows 7.
See
Windows Live Mail Hate - 83% People Agree (96 opinions) for opinions about the rubbish 'Windows Live' hippy-village 'share everything with everybody' cr@p which Micro$oft seems to expect everyone to use now....
Only other options are:
Outlook (which isn't free, of course)
A non-Micro$oft e-mail system
I cannot believe that Micro$oft were such complete and utter idiots as to turn their back on the quick and simple Outlook Express....
They have alienated thousands of customers as a result.
The only options are to