avast internet security 5.0.418 crashed xp pro sp3

i have windows xp pro, sp3, fully up to date (except for feb 10 security updates, as my network services failed after this update) running an iis 5.1 web server. I have had avast pro 4.8 running for years, no problems, so I thought I’d update to internet security 5, as I bought it for my laptop and it was a 3 pc license. My 4.8 pro version on the desktop still has 6 months to go so I can wait for a fix, however, this is what happened:

I install avast internet security 5.0.418, restart computer, all works fine for a while, updates are downloaded and applied, then a final restart, and I don’t even get the windows xp boot loader! only norton ghost came up, so I used it to restore to previous working version, and now I have no problems again.

Can anyone suggest anything, is this new version only compatible with Windows 7? It would seem so to me.

Trent.

welcome to the forum. try to do a clean installation from scratch does it work then? if not write back.
good luck.