ntuser.dat?

[LordofEchoSide]

I had this file in my C: drive today, it was never there before. So I deleted it. I restarted my computer and it still works fine. what is this file for?

[DilLy]

That's a completely normal file that is usually hidden on default view settings. I don't know what the consequences are of deleting it, it might even recreate itself.

But you might want to watch what you delete, lol.

[pointd]

It is not usual for this file to be in the root of the c: drive however you will have a NTUSER.DAT for each user of the computer. This file is read into the HKEY_CURRENT_USER section of the registry when a user logs on and contains all their personal setting for screensavers etc, recent Run lists and all the other bits of personalised data. At logoff the HKEY_CURRENT_USER hive is saved to this file and stored until the next time the user logs on.

If it is deleted a new one will be created from the copy stored under the Default User.

[doctorgonzo]

There is a copy of NTUSER.DAT under C:\Document and Settings\user for each user. As long as you have those files in those locations, you should be fine. I once found a copy in a weird location as well, and deleted it with no problem.