Be Excellent To Each Other

Anyone ever come across this?
My Dad's PC won't boot unless he uninstalls his antivirus program. As soon as I reinstalled it, it gets as far as the XP logo and reboots going into a loop. Uninstall the program and it boots fine. Tried with Avast and AVG.

Have also done a system restore to well old time and behaviour is still present. Cannot nuke and pave as his copy of windows is hooky despite him buying from what he thought was a decent independent shop.

Hate to say it but a virus is the most likely thing - try going to one of the online virus check websites and see what it throws up (Trend housecall?)

My thoughts would be the AV when its starting is finding and blocking something it doesnt like thats hooked into a system file and because windows cant load that system file its bouncing.

(Could be other things but the suggestion it works fine without AV makes me think its something nasty)

Yep, did an online scan and it found a Trojan. Cleaned that out for me. Then tried reinstalling Avast and same prob. Can boot into safe mode so now scanning with Avast from there.

Might buy them a genuine XP disc just so I can install MSE and not worry any more.

Safe mode scan found nothing. Scheduled a boot time scan and it still loops. Annoying.

Okay so my next thought would be something which is hiding (rootkits hide themselves from the OS) - I'm not sure if there are any free ones out there but before you go down the cleaning route I would suggest backing up anything you want to keep from the machine and rebuilding the OS

That's my thought. The rebuild, not the rootkit bit, just need to fund a legal copy of XP!

That's my thought. The rebuild, not the rootkit bit, just need to fund a legal copy of XP!

Check your PM's for the other bit (not the legal copy of XP)

And then, when you've done the rebuild, run your browser inside Sandboxie!

I've been running that on my machine since you said about it, and in fact did actually tell my dad I'd be putting this program on. Sandboxie's a perfect little yellow bundle of awesomeness.

Could always have a go it with clamav on the Knoppix STD livecd, that'll keep you going until you can nuke it & even if it doesn't work you can back up anything important from it.