Overview: we recommend performing both a VIRUS scan AND an ADWARE scan; although "adware" is classed as harmless some of these apps can cause loss of functionality and even harvest data - get rid of them!
Trend HouseCall - Free Online Virus and Spyware Scan
This service is provided by Trend Micros (business-class security company with an excellent reputation). Just click the link below to visit their website and click "start scan" - a small file will download from their website and begin a very thorough scan of your system.
Lavasoft Ad-Aware Free Antivirus+
Lavasoft have a long history of providing services to root out adware and malware, and still offer a free version of their product for download. Just click the link below to download their free version, and then perform a full scan of your system.
And for complete peace of mind...run an additional scan using SpyHunter: https://www.enigmasoftware.com/products/spyhunter/