Malwarebytes said to be present when it is not found

I installed Bitdefender as I could not open two documents in Word at the same time, nor could I add an attachment to email in Thunderbird. I therefore suspected a virus. Bitdefender scan showed nothing, but next time I booted the computer it said (before Windows came up) that it had cleaned many but not all files.

As the problem with Word persisted, I also installed Malwarebytes and scanned. It found many keyloggers which were quarantined. The problems with Word and Thunderbird persisted, so I uninstalled both Malwarebytes and Bitdefender. I am now trying to re-install Bitdefender but it tells me that Malwarebytes is present although I can find no trace of it on the computer. I need advice but not too soon as I will need a break now. If there is no simple way of installing Bitdefender I will need to know that as I only have one life and would not want to persist with it.