How can Protect Computer?

Hi ,

I have been using internet last 6 months in many different kinds of work, such as uploading image, video or downloading software, video as my business requirement. I have noticed some issue with my pc, restart some time, slow speed, etc. I think it is happening by viruses.

I just want to know how can i protect my pc by various viruses and make it safe. Please if you have any kinds of suggestion, let me know.

Thanks,
Acai Juice