You didn't tell if this was XP Home or Pro so I'm going to give the XP Home answer.
Step 1. Boot XP Home in SAFE MODE and login with the Administrator account. If that works, proceed to step 2.
Step 2. Create a new account and move the files from the failed account to the new account using this link -> http://support.microsoft.com/kb/811151
Bob
As a result of trying to remove a virus from my machine, I am no longer able to log into the PC. When Windows boots up, I get a prompt to login as either of two users I have setup, both do not require passwords. I select either user, it says logging in and then says logging off and returns me to the same screen to select the user.
I was able to install a fresh copy of XP in another folder and get access to files and folders, scanned for viruses and did not find any. However, I really would like to get the older installation working again. Also, how can I access my older Outlook emails, I could not find any PST files on the PC.
Any ideas how I should try and resolve this?

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