OneCare has been replaced by "Security Essentials".
http://www.microsoft.com/security_essentials/
OneCare doesn't support Win7, Security Essentials does.
Just caught this, this morning before installing W7.
If you are using Windows One Care, still... read this link below...
Apparently W7 won't recognize your backup files, done with One Care after you install W7! Unbelievable!
http://support.microsoft.com/kb/968420

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic