Can't login in Safe mode

[Jolie-Pitt]

I run windows xp in my system and i have installed Symantec Antivirus software. Today it has reported Trojan horse. I have gone through some article for removing Trojan, they have suggested me to boot in to safe mode. However i am not able to boot in to safe mode, it comes up with CNTRL, ALT, DLT screen. I have tried entering the username and password but its not accepting it. I want to know what might be wrong in my case???? I am quite sure that i am entering right username and password.

[Billie]

If its your standalone machine and not domain member one than you can type "Administrator" as username and leave the passowrd field blank for logging in. If its a domain member machine than you might not be having local user account and that's the reason your usual name/password isn't not getting accepted, in that case you will have to contact your systems for logging in as local
Administrator.