Before anything disconnect the Internet connection line and use F8 when the
computer is coming on to start in Safe Mode, (press F8 about 3/4 times) If
you can't logon that way try the Last known good configuration option,... if
you can logon in any of those ways, run antispyware programs and go to
Windows
Explorer\Tools\Folder Options\View\and uncheck "Use simple file sharing
(recommended)". Next go to C:\Properties\Security
tab\Advanced\Options\Owner\and make sure the administrators group has
ownership of the system and if not so add the group of personal account as
owner. Next see if any unknown account is present in the C:\drive security
among the user groups. Default accounts are Administrators group, Creator
Owner, SYSTEM, an limited users... remove any other unknown account if
present.
If you don't have antispyware programs installed and you need to download
them, logon in the Safe Mode with Networking option to access the internet,
but first check the Security settings in the C:\Properties... and also check
in Start\Run\type; msconfig and hit enter, in the Startup tab, look for
unknown processes that may be a malicious program that may have taken
control of your system. Normal processes in msconfig should be; the
antivirus, the MSOffice taskbar, and messenger... disable by removing the
check mark, apply and exit... next go to Start\Run\type; regedit and hit
enter and go to the Run registry keys and delete any unknown process that
again may be a hijacker... Normal values in the Run keys are: a default
value, the antivirus value(s), the msoffice value, the messenger value and
the CTFMON value... delete any other value which could be a hijacker.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
The programs you need to install are.
Adaware SE Personal, Spybot Search & Destroy, SpywareBlaster and CWShredder
http://www.majorgeeks.com/downloads31.html
How to take ownership of a file or folder in Windows XP
http://support.microsoft.com/kb/308421/en-us
Describes how to take ownership of files or folders that you may not have
permissions for if you are an administrator for that computer.