Free from virus again

I love the performance of my Acer Aspire laptop now because it is faster than before. two weeks ago, I went to the Columbia Computer center where I bought my laptop to have my laptop check. My friend Tristan, a computer technician who worked in the said store told me that my laptop has a virus already and we need to reformat to clean the system. Tristan reformatted my laptop and I am so satisfied with the result because I can browse and navigate with my laptop easily and it is more faster to open programmes and sites. I am now so careful with the sites that I visit because I don't want to see any virus again in my laptop.