probably not a virus, just pop ups or something enabled in your browser. Go through your browser and get rid of any settings that look like that. Clear your cache in the browser for all time, click all the boxes.

What does the storage space look like?

How old is the pc? If it’s older than 7 years then yeah just get a new one.

I would look in storage settings. It shows the break down of what’s holding all your data in simple terms. You might be surprised and find some unimportant things you can delete. Good luck 👍