Etienne, it's nice that maybe in 250 cleanings, you believe you have not run into rootkits but, to my knowledge, MBAM does NOT clean rootkits - it can clean some virus, spyware and other malware - rootkits are very specialized software and, even IF it happens to 'clean' - then the cleaning is still suspect.

I will repeat again, for everyone's edification: IF there is ANY suspicion of a rootkit on your system, the ONLY viable action is KILL the drive, then REBUILD the drive. You can play with 'cleaning' techniques but, even if the rootkit is recognized and 'claimed' to be cleaned, there's no way to know for sure except rebuild the drive.

And BIOS rootkits and viruses are even more problematic (yet, thankfully much more rare).