I'm just finished tuning nnCron under windows 7 home premium 64-bit, so I can write what I did step by step:
1.Downloaded last nnCron beta from here: http://www.nncron.ru/download/nncron193b10.exe
2.Then I just coped newest files into existing cron directory (backup is aways good)
3.Checked that nncron.exe, tm.exe, nnguard.exe runs with administrator privileges (compatibility tab)
4.Created shortcut in windows start menu that starts nncron with parameters: D:\WINCMD\cron\nncron.exe -ns -dir D:\WINCMD\cron
5.Made small modifications in crontabs (deleted option AsLoggedUser from all tasks) because of nnCron runtimes errors.
So it seems nnCron works under Win7 HP 64-bit just fine, but not as a service rather as application which starts and works under current user session.
There is a way to start nnCron as service but my method works just fine for me.