You should all know about the good free software that is available to you out there, so I've created a little list of things you could download for your computer.
Like any software, please be careful using software that you download...if you are unsure of usage, please seek technical help from a professional.
Malware Bytes Anti Malware - One of the best tools to remove nasty malware infections from your computer.
Notice I haven't listed an Antivirus? Virtually all systems today have built in FREE antivirus, don't be conned by 3rd party crap advertisers, Norton, McAfee, Kaspersky etc. are all out to make money, and lots of it through fear of media. Most internet providers provide additional virus scanning at server level, and not forgetting you not only have a software firewall built into your devices but also a hardware firewall in your router.
If you really need the reassurance of a 3rd party antivirus, then pay for Bullguard Internet Security, it's the only one I would personally recommend and buy.
Defraggler - This is the fastest defragging software available, this keeps your hard drive in prime condition. NOTE: Please do NOT use defraggler on SSD drives, instead Google how to use TRIM for SSD's instead.