Having antivirus installed in computers is the first key to prevent malware infection, even though they cannot fully protect your computer. Carefully read what is being downloaded from the internet will ensure the safety. Consider using cloud storage or e-mail to secure files instead of portable data storage (flash drives or external hard drives) for more security since almost trustable cloud and e-mail services such as Dropbox, Hotmail, or G-Mail have strong integrated malware detection systems. Using hard drive freezing software such as the Deep Freeze could be the best method to secure your computer, but you need a place to secure your user-created files however. This kind of freezing software will roll back your PC to the initial state at every system restart, deleting all newly-created things including malware. It is better use with cloud storage system for maximum safety and convenience.