All day every day I get pop-up messages that tell me it has found critial system errors and that if I don’t repair them then my computer might…(everything bad). when I visit the website on the message it wants me to buy a clean-up program. Do I need this?

….It started happening about two months ago…a little after it started I had a system crash due to power outtage and had to reboot from original shipped files….it still popped up…I have tried system restore a few times….but hasn’t worked.
…I am connected to the internet at start-up(roadrunner)…but it does pop up even when not using internet

…….any recommendations?????????

registry repair