There's no excuse for not using an antispyware program these days. Having one of these programs can help with spyware infestations. Whereas antiviral programs have a definitions database which focuses primarily on malicious programs, antispyware programs concentrate on ad-based trojans and malware. Makers of antispyware are able to focus more in depth on the latest adware-based attacks. Antivirus makers don't have that luxury and need to focus on more broad targets and may run a step or two behind catching the latest spyware threat.
There are a few very good free antispyware programs. Namely, MalwareBytes, Superantispyware, and Spybot Search&Destroy. The only problem with these freeware versions is that they don't offer real-time or scheduled scanning. In other words, they only help with removal after your computer has been hit with a piece of malware; however, MalwareBytes and Superantispyware do offer paid versions which have these features and more. In addition, paid versions may offer a few more bells and whistles such as registry backup and repair and USB protection.
The other type of antispyware many people use is the purchased kind. Brands of this kind include Webroot's SpySweeper, iS3's StopZilla, and PCTools Spyware Doctor. All of these make for excellent antispyware programs not just for removal but also prevention. With features such as scheduled scans, real-time protection, web browser protection, and more, this type of software should keep you safe from an attack before it happens. Much like antivirus software, antispyware software has a set of definitions that are regularly updated which scan for the latest threats. Be sure to check often for updated definitions to ensure your computer's safety.
How do you know which version is best for you? Much of your decision should be based on your familiarity and experience with the internet. If you are familiar with how viruses and spyware are transmitted and don't visit so-called 'social' sites and if you are able to identify legitimate emails and their attachments as being harmful, perhaps the free versions of antispyware will suffice. Just be sure to run regular scans with them to ensure your computer is free from malware.
With today's vast selection of antispyware and antivirus software; whether it be subscription-based, paid, or free, you should be able to protect your computer and personal data from harmful internet threats. If you still aren't sure which product to use, bear in mind that many vendors offer free trial downloads of their software. Don't get caught without adequate protection.