With increasing technologies, there are increased threats of virus and various other issues. We generally get worried on even small issue with the computer/PC. The best way is avoid all these by taking some careful steps:

1. Keep some free space in the hard drive.
2. Format your system at least twice in a year. Don't wait for a problem to occur to format.
3. Keep firewall updated.
4. Install anti-virus (only 1) and keep it updated.
5. Use the operating system that is supported by your computer/PC, i.e as per RAM size.
6. Scan every program before you run it. For this, use firewall command.

For any problem that occurs, there is online computer support service available widely today. You can take their help if any problem still occurs.