My laptop's about 2 and a half years old. I use it a lot and over the past couple of months it's been getting slower and slower, very noticeably so in the last few weeks. I always install Windows Updates and I use BitDefender to protect it. At the moment my C-Drive has only 2.26 GB of 66.7 GB free. It takes minutes to open IE and it has difficulty opening every new tab. Once I get to a website it's not as bad, although nowhere near as fast as it used to be.
So basically, what steps should I be taking to a) reliably ensure there's no viruses or spyware on my laptop and b) make it run faster?