A large number of computer/hardware issues are resolved by simply rebooting (or restarting) the machine. However, if you continue to have issues after rebooting it could be a sign of more serious problems.
Virus Definitions, are they important?
The key to being properly protected from viruses, malware, trojans, etc. is to have the most up-to-date virus definitions. These definitions change daily and keep you protected from new malicious software threats.
Have you backed up lately?
Having the proper backup can save you from the heartbreak of losing invaluable files due to hardware failure, lightning, and even fire.