VeraCrypt This succesor to the well-regarded TrueCrypt creates virtual disk drives in encrypted “container” files. Can also encrypt whole disks and partitions - including some boot drives. Unless you do something stupid, even three-letter government agencies shouldn’t be able get your data.  Security is even better after updates following code audits of both TrueCrypt and VeraCrypt.
  Password Safe Lets you remember just one (strong) password for the safe and then store your other passwords inside. The encrypted file can then be backed up and copied anywhere. Much better than writing passwords on a post-it stuck to your monitor.  There are many password "lockers" like it, but this was one of the first - originally written by Bruce Schneier back in 1999.
 DBAN Permanently nuke the contents of a hard drive by overwriting it multiple times with random data.
(bootable CD).
Unless you used whole-disk encryption or physically destroy the drive, the next owner could be looking at your personal stuff.  While disk sector remapping and SSD wear leveling can make this less than perfect, it is certainly better than nothing.
 Comodo Comodo Internet Security is a firewall and real-time malware detection combo. The anti-virus component is optional - but obviously recommended. While the firewall is very good, its security warnings are a bit intrusive unless you adjust its sensitivity. BTW, Comodo also offers a variety of other free (and non-free) security tools here.
 ClamWin This ClamAV-based tool complements your existing real-time malware detection tools with scheduled virus-scans. Definitely not a "first line defense" but it never hurts to have a second opinion. If you want three, four, or more opinions submit your file to over 50 different scanners at Virus Total.
 Kaspersky Rescue In case malware has gotten to your operating system, this can scan and clean your system without booting the potentially infected OS.
(bootable CD).
If you don't like Kaspersky, there are links to other rescue disks here.