How do you think, what can be the problem: I'm 100% sure that I input correct login and password but I cannot to pass authentication on some sites (not all).
I have a sony vaio laptop and I've just reinstalled Windows (now I have Windows 7).
Check your language settings. It is possible that your newly installed Windows uses a different keyboard layout than the previous installation.
This can occur if, for example, your old installation was German and you forgot to specify German keyboard layout in the new installation. Normally you would notice something like that quickly, but if it's not US/German but perhaps US/UK then the difference can be small - but just might affect the placement of characters you only use in passwords!