I found a link that repairs the xp registry on the mcafee forum at communit.mcafee.

deletemalware.blogspot.com/2011/06/remove-xp-antispyware-2012-xp-internet .html

I scanned it with avast before copying to my pc and merging with my registry.

it has re associated my file types so that they run, however i have a message from the real windows security program that my auto updates is turned off. When I check in system in control panel they are turned on so thats apain, but i can live with it.
Also avast no longer starts automatically.

Apart from these problems pc is ok (don’t know why mouse is suddenly ok - it was working before i applied registry fix)
I have now installed ccleaner from piriform and running a registry scan.
(be careful with ccleaner as the default settings will remove some stuff that you might want to keep)
After running ccleaner registry fix, avast and other startup progs run properly.

Thanks Bob pointing me to malware bytes.