OneCare should not be impeding the use of your PC unless you also have other security software on the computer which is conflicting with it. You should only have one security suite providing active protection installed or you will have problems.
If you prefer to remove OneCare from the PC, see this post:
How to Uninstall Windows Live OneCareDisabling it would be pointless, as the purpose of OneCare is to provide protection to the PC. If you have a specific need to disable OneCare protection temporarily, you can do this on the tabs for the Firewall and Virus/Spyware Protection under Change Settings when you open OneCare by double clicking the tray icon.
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator