See details at https://www.its.hku.hk/faq/personal/software/virus
Perform Windows Update once a month to download and install the latest security patches by clicking the Windows Start => Windows Update.
Install anti-virus software and update your virus definitions daily and set scheduled scans of your PC.
Install an anti-spyware software on your PC.
Do not open any email attachments even from people you know because the senders' names can be spoofed. You can verify the attachment with the sender first or scan the attachment before you open it.
- Do not give your email address to any internet subscriptions unless you know they are a trustworthy site.