computer issues of a friend of mine

Okay my sister is having some major issues with her comp so I am trying to relay whatever she gives to me onto you in hopes you may be able to help her out.computer system properties
microsoft windows xp
professional
version 2002
computer
Intel(R)
pentium(R) 4 CPU 2.80GHz
2.81 GHz
1.00GB of RAM

when she starts her comp up it has like this ms dos thing that goes off fast but it says C/windows/system32/chcfg.exe.
When she logs off it has a error popping up that says mediaacck.exe failed to start and thats all she can get of it before it closes.

It keeps changing her homepage and has serious issues with yahoo and everything to do with yahoo.She says that the dll files keep coming up as missing or no longer valid and she has been unable in all her attempts to find her windows folder. So I am asking you what is your opinion. Is there any hope for it, is it some kind of virus that will need to be reformatted or could it be adware problem that she can get rid of. She said something about aurora I am unaware of what that is so I am hoping someone out there can give me an idea of what to do next. I had her copy what was in her HKEY_LOCAL_MACHINE\SOFTWARE folder to see if that might help with this situation. she came up with the following:
HKEY_LOCAL_MACHINE\SOFTWARE\Acudata
HKEY_LOCAL_MACHINE\SOFTWARE\Adobe
HKEY_LOCAL_MACHINE\SOFTWARE\Ahead
HKEY_LOCAL_MACHINE\SOFTWARE\ALWIL Software
HKEY_LOCAL_MACHINE\SOFTWARE\Apple Computer, Inc.
HKEY_LOCAL_MACHINE\SOFTWARE\ATI Technologies
HKEY_LOCAL_MACHINE\SOFTWARE\ATI Technologies Inc.
HKEY_LOCAL_MACHINE\SOFTWARE\Avance
HKEY_LOCAL_MACHINE\SOFTWARE\BackWeb
HKEY_LOCAL_MACHINE\SOFTWARE\C07ft5Y
HKEY_LOCAL_MACHINE\SOFTWARE\Calculator
HKEY_LOCAL_MACHINE\SOFTWARE\Canto
HKEY_LOCAL_MACHINE\SOFTWARE\Classes
HKEY_LOCAL_MACHINE\SOFTWARE\Clients
HKEY_LOCAL_MACHINE\SOFTWARE\Creature Labs
HKEY_LOCAL_MACHINE\SOFTWARE\CurrentControlSet
HKEY_LOCAL_MACHINE\SOFTWARE\CyberLife Technology
HKEY_LOCAL_MACHINE\SOFTWARE\CyberLink
HKEY_LOCAL_MACHINE\SOFTWARE\Description
HKEY_LOCAL_MACHINE\SOFTWARE\Gemplus
HKEY_LOCAL_MACHINE\SOFTWARE\General
HKEY_LOCAL_MACHINE\SOFTWARE\GIGABYTE
HKEY_LOCAL_MACHINE\SOFTWARE\Grisoft
HKEY_LOCAL_MACHINE\SOFTWARE\IBM
HKEY_LOCAL_MACHINE\SOFTWARE\InstalledOptions
HKEY_LOCAL_MACHINE\SOFTWARE\InstallShield
HKEY_LOCAL_MACHINE\SOFTWARE\INTEL
HKEY_LOCAL_MACHINE\SOFTWARE\Licenses
HKEY_LOCAL_MACHINE\SOFTWARE\Logitech
HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia
HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins
HKEY_LOCAL_MACHINE\SOFTWARE\NCSoft
HKEY_LOCAL_MACHINE\SOFTWARE\Nico Mak Computing
HKEY_LOCAL_MACHINE\SOFTWARE\NVIDIA Corporation
HKEY_LOCAL_MACHINE\SOFTWARE\ODBC
HKEY_LOCAL_MACHINE\SOFTWARE\Policies
HKEY_LOCAL_MACHINE\SOFTWARE\Preview Systems
HKEY_LOCAL_MACHINE\SOFTWARE\Program Groups
HKEY_LOCAL_MACHINE\SOFTWARE\QuickCamInstallTemp
HKEY_LOCAL_MACHINE\SOFTWARE\Realtek
HKEY_LOCAL_MACHINE\SOFTWARE\Realtek Semiconductor Corp.
HKEY_LOCAL_MACHINE\SOFTWARE\ReFog SOFTWARE
HKEY_LOCAL_MACHINE\SOFTWARE\RichFX
HKEY_LOCAL_MACHINE\SOFTWARE\Schlumberger
HKEY_LOCAL_MACHINE\SOFTWARE\Secure
HKEY_LOCAL_MACHINE\SOFTWARE\ShudderLTD
HKEY_LOCAL_MACHINE\SOFTWARE\Street Source LLCH
KEY_LOCAL_MACHINE\SOFTWARE\Sun Microsystems
HKEY_LOCAL_MACHINE\SOFTWARE\SurfSideKick3
HKEY_LOCAL_MACHINE\SOFTWARE\Symantec
HKEY_LOCAL_MACHINE\SOFTWARE\The Silicon Realms Toolworks
HKEY_LOCAL_MACHINE\SOFTWARE\TuneUp
HKEY_LOCAL_MACHINE\SOFTWARE\Viewpoint
HKEY_LOCAL_MACHINE\SOFTWARE\SurfSideKick3
HKEY_LOCAL_MACHINE\SOFTWARE\WDIG
HKEY_LOCAL_MACHINE\SOFTWARE\WildTangent
HKEY_LOCAL_MACHINE\SOFTWARE\Wise Solutions
If there is something there that can be messing with her comp then please let me know. And what to do to get rid of it or if she has to go elsewhere to look for the problem. I appreciate this but I'm sure she will even appreciate it more.