How to remove a virus from your computer – expert tips

Viruses and malware are a serious threat to your computer, your data and your privacy. If your computer shows signs of infection, it is important to act quickly. In this guide you will learn how to recognise an infection, how to remove it and when it is time to call professional IT support.

Signs your computer is infected

How can you tell if your computer is infected? These are the most common signs of a virus or malware infection:

• A slow computer: A sudden drop in performance, programs open slowly and the system freezes
• Pop-ups: Constant pop-up windows and ads, even when you are not browsing
• Unknown programs: Programs you did not install appear in Task Manager or the Start menu
• A changed home page: Your browser’s home page changed without your knowledge
• Antivirus turns off: Your antivirus shuts down by itself or cannot update
• Strange behaviour: The computer restarts by itself, files disappear or new ones appear
• Overheating: The fans run at full speed all the time and the computer gets hot
• Messages to your friends: Your contacts receive strange messages you did not send
• Ransomware lock screen: A message saying your files are encrypted, with a ransom demand

Types of malware and viruses

There are several types of malicious software, each with a different goal:

1. Viruses

Classic viruses attach themselves to existing files and programs and spread when someone runs an infected file. They can damage data, slow down the system or give attackers access.

2. Trojans

Trojans pose as legitimate programs, but in the background they steal data, track your activity or open a “backdoor” for attackers. They often arrive through email attachments or fake downloads.

3. Ransomware

Ransomware encrypts all your files and demands payment (usually in bitcoin) to decrypt them. It is one of the most dangerous threats, because without a backup you can lose everything.

4. Spyware and adware

Spyware secretly tracks your activity, passwords and card details. Adware floods your computer with ads and slows it down.

5. Rootkits

Rootkits embed themselves deep in the system and hide from antivirus software. They usually give attackers full control over the computer.

6. Cryptominers

They use your computer’s resources (CPU, GPU) to “mine” cryptocurrency without your knowledge, causing overheating and high power consumption.

How to remove a virus yourself

If you suspect an infection, here are the steps you can take yourself:

Step 1: disconnect from the internet

Turn off Wi-Fi or unplug the network cable straight away, to stop the infection spreading to other devices on your network and to prevent data theft.

Step 2: start Safe Mode

Restart the computer in Safe Mode:

1. Press Windows + R and type msconfig
2. Open the Boot tab
3. Tick Safe boot and choose Minimal (remember to untick it again after the clean-up)
4. Click OK and restart the computer

Step 3: delete temporary files

Viruses often hide among temporary files. Delete them:

• Press Windows + R, type %temp% and press Enter
• Select all files (Ctrl + A) and delete them (Shift + Delete)
• Repeat with temp (without the % signs)

Step 4: run an antivirus scan

Run a full scan with your antivirus. Recommended free tools:

• Microsoft Defender: Built into Windows, excellent basic protection
• Malwarebytes: The free version is great at detecting and removing malware
• ESET Online Scanner: A free tool for a one-off scan
• HitmanPro: A free 30-day trial

Step 5: uninstall suspicious programs

Go to Control Panel > Programs and Features and uninstall any program you do not recognise or did not knowingly install.

Step 6: reset your browser settings

Viruses often change browser settings:

• Chrome: Settings > Reset settings > Restore settings to their original defaults
• Firefox: Help > More troubleshooting information > Refresh Firefox
• Edge: Settings > Reset settings > Restore settings to their default values

Step 7: update Windows and all your programs

Install all Windows updates and update all your programs. Many viruses exploit security holes in outdated software.

When should you call a professional?

Sometimes removing a virus yourself is not enough or not possible. Contact an IT technician if:

• Your antivirus cannot remove the virus, or keeps turning itself off
• Ransomware has encrypted your files
• The computer cannot start, or keeps crashing with a blue screen (BSOD)
• You suspect sensitive data was stolen (passwords, banking details)
• The virus keeps coming back after removal
• You have important business data you do not want to risk
• You lack the technical knowledge or are not confident doing it yourself

Prevention – how to protect your computer from viruses

The best defence is good prevention. Follow these tips:

1. Use a good antivirus

Install a reliable antivirus (Microsoft Defender, Bitdefender, ESET) and keep it up to date.

2. Keep your system updated

Turn on automatic Windows updates. Attackers often target old, unpatched systems.

3. Be careful with email attachments

Do not open suspicious attachments, even if they come from people you know. Always check first.

4. Download only from trusted sources

Avoid pirated software and free download sites. Download programs only from official websites.

5. Use a firewall

Windows Firewall provides basic protection. Always keep it on.

6. Back up regularly

A backup is your best protection against ransomware. Follow the 3-2-1 rule.

7. Use strong passwords

Use a different, strong password for every account and consider a password manager.

Conclusion

A virus infection can happen to anyone, but a quick reaction and the right removal steps can save your data and your computer. You can remove some infections yourself, but more complex cases need professional help. Perfect Light in Zagreb removes viruses and malware remotely or on site – in English or Croatian – and sets up protection so the problem does not come back.

Remember: prevention is key! Regular backups, a good antivirus and careful browsing can save you a lot of headaches and money.