Hi Tamás,
I don't use Win 7 but what I'd suspect, maybe your memory is not too much either. I know that Vista is rather memory hungry and though Win 7 is said to be a smoother OS, I doubt that they have tweaked it too much in the direction of using less RAM.
What Remus says - autosaving - sounds reasonable and maybe some more memory would help with this issue.
Ha nem gond, közben hozzáadtalak a magyar felhasználói csoporthoz, ha "odalent" a Magyar Fórumon is körül akarnál nézni.
😉