Thanks whocares,
winusr.exe posted to virus (at) avast.com

I was already using SpywareBlaster & PestPatrol and scan is clean
scan by Spybot - Search & Destroy done: clean

On-line scan by “COD Command On Demand” clean

On-line scan by “Trend micro” clean
http://fr.trendmicro-europe.com/enterprise/products/housecall_pre.php

On-line scan by “Panda active scan” clean http://www.pandasoftware.com/activescan/fr/activescan_principal.htm

On-line scan by “kaspersky” clean
http://www.kaspersky.com/fr/scanforvirus

Of course, no reference to winusr in regedit or in Hijackthis except the win.ini