Windows Xp conflict

I’m new to forums so please forgive me if this message is out of context.

I recently downloaded Avast free antivirus to my desktop which uses windows XP.

Then, the system logged off and won’t let me back in.

The system seems to be caught in a loop.
After switching on the computer asks me for login details. User name and password.
I don’t know what to do to.

Can anybody help please

Spiros, do you have any other antivirus installed in this machine?
Can you boot Windows in Safe Mode (pressing F8 while booting)? If so, you can uninstall one antivirus (or other program that is conflicting) from there.

I cant boot in safe mode because it asks again for Username and Password >:(
Then I tried the user name “Administrator” but I cant still log in.

Also, I dont have amy other antivirus programms on my computer.

But… Isn’t it the case that you’re witting the name or the password wrongly?
Did you forget the password?

But I didnt give any user name or password

Well… You should to start (install) Windows… It could have automatic login, but you need an username and password in Windows XP.
There are brute force ways to crack the Windows password (http://ophcrack.sourceforge.net/).

Well it seems difficult to me to use this programm

Yes. It’s not simple… you need to burn a CD within another computer and try to discover which is your forgotten Windows password.

So, I tried other programms which I found on the internet (like Windows Key Password Reset) but it didn’t work.
Also, when I tried to connect as “Administrator” a message poped which said “Unable to Log You on Because of an Account Restriction”.

I’ d like to know where I can find instructions for the program you suggested me

http://sourceforge.net/apps/mediawiki/ophcrack/