Malware can come from a number of places. Downloads, webpages, File Sharing, and so on.
If everything is good then:Create a new Restore Point
to prevent possible reinfection from an old one
. Some of the malware you picked up could have been saved in System Restore. Since this is a protected directory your tools cannot access to delete these files, they sometimes can reinfect your system if you accidentally use an old restore point. Setting a new restore point AFTER cleaning your system will help prevent this and enable your computer to "roll-back" to a clean working state.
The easiest and safest way to do this is:
• Go to Start > Programs > Accessories > System Tools and click "System Restore".
• Choose the radio button marked "Create a Restore Point" on the first screen then click "Next". Give the R.P. a name, then click "Create". The new point will be stamped with the current date and time. Keep a log of this so you can find it easily should you need to use System Restore.
• Then use Disk Cleanup to remove all but the most recently created Restore Point.
• Go to Start > Run and type: Cleanmgr
• Click "Ok"
• Disk Cleanup will scan your files for several minutes, then open.
• Click the "More Options" Tab.
• Click the "Clean up" button under System Restore.
• Click Ok. You will be prompted with "Are you sure you want to delete all but the most recent restore point?"
• Click Yes, then click Ok.
• Click Yes again when prompted with "Are you sure you want to perform these actions?"
• Disk Cleanup will remove the files and close automatically.