recommendations for free scanner ?

Kaspersky Virus Removal Tool mainly and you can stop here, avz by oleg (outdated but can give some insights, and its good to know which programs are suspicious or potentially dangerous), ESET online scanner (great for PUP detection), Emsisoft emergency kit, VIPRE Rescue, Sophos Virus Removal Tool , hitman pro with early detection on, NVT Malware Remover will pick up some native Windows files that can spy it is massively outdated), RogueKiller is ok too but has tons of FP. Norton power eraser is aggressive too and will pick up alot of legitimate programs. Farbar can be very useful

aside from that you have some interesting scanners with native live programs, ie qihoo360 will scan certificates, or avast will scan network and scour if there are PPI files

These are the tested ones, offline scanners are a waste of time though as the attacks are very persistent effective and integrate perfectly, if OS is not trustworthy it is better to wipe and reinstall or better sell/destroy and buy new, relying on VM on clean OS is the way to go, that and tons of other barriers (especially focused on networking like blackfog and eset with firewall) and common sense