Hello littlepanther
I think this is a malware problem and it`s hard to fix it if you cannot run any programs.
See if you can boot into Safe Mode by pressing F8 continually during boot up.
There should be a Welcome Screen with your Account and the "Main Admin" Account. Try to access the "Main Admin" Account. Just press Enter when asked for a password if you did not set one at the installation of XP.
If you get in, can you do anything here?
Also at the Safe Mode Options screen select
'Safe mode with command prompt'
At the command prompt type
C:\Windows\system32\restore\rstrui.exe
Hopefully this will open System Restore, so restore to before the problem started
http://bertk.mvps.org/
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