Registry Data Items Infected

Every couple of weeks my computer all of a sudden starts to go really, REALLY, slow. I run Malware Bytes program and I get this same message every time:

Registry Data Items Infected:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center\AntiVirusDisableNotify (Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Quarantined and deleted successfully.

I let Malware clean it up and my computer works great only to do this again in a couple of weeks. Is there a way I can prevent this from happening? I'm not even sure what the registry is. I have an anti-virus and it's on so I can't figure out why this keeps happening. Any help would be appreciated! Thanks.