Most PCs are connected to the Internet and networks, making easier the spread of viruses, trojans, spyware, rootkits, worms and other malicious programs. They can get into your computer in a number of ways, including via your web browser, e-mail, or in a bundle with a software that you download from the Internet.
The best way to protect yourself is with a virus or malware scanner. Emsisoft Anti-Malware (previously known as a-squared Free) is a program that can be a good choice to scan and remove malicious software from your PC. The new version comes with great improvements and completely re-written dual scan engine for multi-core optimizations which brings a huge speed improvement on average, with the same things being scanned. Also, the false positive handling was improved too and now with the latest version, there is a caching system which makes the scanning faster with every scan.