Badly Infected Computer - Cannot install AV

[yumpum]

Hello Everyone.

I am currently in the process of fixing a friends Laptop that is badly infected with who knows what.

Unfortunately, He did not have any anti virus installed, and it now appears impossible to install any.

I can:
Boot into normal xp and safe mode
get onto the internet if I plug the laptop directly into the rotuer
open cmd, my computer, control panel (with limitiations)

I cannot:
Install most anti virus software. I get some form of error with all of them.
See the start bar (It's hidden out of view)
Use the 'search' function
open many programs including IE (got MF though)
many other random things

I have tried:
running combofix, it says a system file is infected (regedit) and then installs something from the windows website to install it, however that fails to fix the problem.
running chkdsk
running spybot s and d


I am fairly sure I am blocked from changing any services or anything, the virus has stopped me changing startup options, and often i can't close windows.

Any help is much appriecated.

Thank you

 

[hang-the-9]

Malwarebytes run well in SafeMode.

Make a book CD from here http://www.ultimatebootcd.com/, it has an Avira Antivir scan in it you can run off the CD without booting the OS.

 

[mary221]

Run Flobo System Repair in safe mode -> Automatic Repair and choose Ultimate Repair.

After that, restart in safe mode and scan with Avira. uninstal it, install Avg, uninstall Avg.

Run Virus Effect Remover.

Start in normal mode and install an firewall.

Let me know if it worked.

 

[yumpum]

Thank you for the suggestions. I will let you know

 

[aford10]

There is a good step by step guide in my signature.