Almost all offers to remove viruses, Trojans and infections are actually infections themselves. There is no way to ensure 100% protection against infections. You can get close to that though. My recommendation is that you install Bitdefender Antivirus Plus 2015. It should be left to automatically update and scan.
I do NOT recommend the use of any product labelled Internet Security or the like. ONLY Antivirus software.
The product will do its own scans. It is very polite and considerate. It will not begin a scan until it “sees” that you have not touched the keyboard or mouse for 10 minutes. Then it will begin a scan, but unobtrusively step aside and suspend itself should you resume use. Then when it has its next opportunity, it will continue.
If you have your computer off for a few days, turn it on and wait a half hour or so to allow them to update themselves before you open any email or use the Internet. The most dangerous threats are the newest ones.
One more tool that is very important to protect you: your good judgment about what and where the Internet is safe. Not unlike taking a walk downtown.
Some Internet activities are more likely than others to lead to infections of malware. Games, video playing/downloading and porn sites are almost sure to infect your computer.
My friend says Apple computers don’t get infected. Not true, but indeed there is a lower probability. Hackers and bad guys that threaten computers will obviously focus on systems they are most likely to find. Since there is about 20 times the probability of finding a Windows computer, that is what they focus on. However, you should not use an Apple computer without virus protection.