Security
It is important that you take this issue seriously. You could easily lose information from your computer which could compromise your financial security, information such as bank details, credit card numbers, etc.
Complex passwords are not easy to remember. Writing them down sort of defeats the point of having a secure password! One solution is to use a program designed to keep private and important data securely.
One such program is Keepass. This is a free program which is a bit like a digital vault. You still need a password to access the vault but you only need to remember one password and even that could be a memorable sentence. Other passwords and financial information (bank account details for example) can be securely held by this program. When you need to use a password from the Keepass vault you can even copy and paste the data you require.
Virus scanner
A virus scanner checks the data stored on the computer looking for programs (viruses) that are designed to do harm in some way. Thes scanner should also check information coming into the computer from other sources, such as the internet, for these viruses.
Passwords
It is important that you take this issue seriously. Passwords must not be simple words that other people can guess, for example your first name or surname or the name of your pet, etc. See the comments above regarding using a package designed to keep passwords secure.