AdwCleaner is a tool that I commonly use to check computers for malware. You can too, for free! It performs one-time scan that won’t interfere with your current antivirus. Simply download it, let it scan, and allow it to remove whatever it deems suspicious. It will also offer to disable unnecessary junk software after it locates any malware.
AdwCleaner may need to reboot your computer as it strips all the junk away, and things may be greatly improved afterwards. But if you notice anything wrong after using this scan-tool, you can always use System Restore to roll back its changes.
AdwCleaner is now owned by Malwarebytes and is available to download here (currently for PC only).
PS: another good one-time scan tool is Norton Power Eraser.