Avas t 7 free crashes and shuts down and restart PC

[Vicky W. Vorney]

Desktop machine with Windows XP Pro. sp3


My PC crashes unexpectedly;  shuts down unexpectedly and restarts automatically; and it starts back on all by itself when I manually shutdown my PC ... all these have been happening since Avast was updated to version 7.
Avast 6 free was very stable.

None of these things happened when Avast 6 was in use.

Help, please.
1. How to avoid these ththings?
2. Where can Avast free 7 be downloaded?

Thanks!

[Asyn]

1. Download avast! Free Antivirus: http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe
2. Follow instructions: http://www.avast.com/uninstall-utility
3. Reinstall avast! with the downloaded installer from point 1.
4. Reboot.

[Vicky W. Vorney]

Thank you, Mr. Asyn.

Four times have been tried exactly in accordance with the instructions and nothing has changed.
Any other ideas, Please?

Thank you very much!

Vicky

[CraigB]

Is there any other security software installed on the system? have you run the correct vendor removal tools to remove remnants of old and factory preinstalled AV's http://singularlabs.com/uninstallers/security-software/

[Vicky W. Vorney]

Thank you, Mr. Craigb.

Yes.  Malwarebytes anti-malware free version.
And Returnil System Safe only its virtualization is applied, not its antivirus.
These were used together with previous versions of Avast and there was no problem at all.

What do you think?

Thanks.
Vicky