One of my friend has below problem.
He can't use his files stored on D. Becuause he was encrypted those files and then reinstalled Xp to C. Now when he opens those files it contains nothing.
Can't he use those files?
Hmm... Not so sure on this topic. Probably find the decrypter for the program you used to encrypt them, then decrypt them. I'm not sure though.
The simple answer is.. NO!!! You have no way to be able to decrypt those files..
When you setup a user account, it has an ID. Something like th UID/GUID in Linux distros... The problem is, you don't know what it is and you Windows doesn't even let you change it...
Now when you make a folder (or a file) private (encrypt), then only you would only have the access to those resources. What happens is that Windows checks if the user trying to access the said resources is really you. Windows does this by checking the "User ID" or whatever it is.
Now when you reformat your disk and reinstall Windows, even if you input the same username and all, you wouldn't likely get the same "User ID"... In that case, you'll never be able to access those files/folders again..
By the way, I think those "User IDs" are randomly generated... So it's very unlikely for you to obtain the same IDs more than once...
Hope that helps...
If so I think encryption is bad thing in windows. Because i will lose all my data if i can't boot windows despite data will reside on other disk.
Yeah man. You should just use 3rd party encryption software... Windows' encryption really sucks.. It doesn't give you full control. I lost gigabytes of data because of that.
He can access those files without a problem. He can use a few tools:
BartPE or any linux livecd (I recommend Knoppix).
BartPE is a windows "livecd" maker and he can make a windows "livecd" and boot it, then move the files on D to another drive or whatever he wants.
As for Knoppix he just has to download, burn and boot. It automatically detects NTFS and FAT drives.