The reason why you are getting the "File or directory not found" message is because you are currently on the wrong path in the command prompt.
Follow the steps for you to be able to the go to correct directory of Windows Live OneCare folder through the command prompt(Dos mode): (Note: All the names that have brackets are the keys found on your keyboard e.g. [Enter]= Enter key)
1) Type in "cd\" then press [Enter]
2) Type in "cd program" then press [TAB], then press [Enter] if the word "program" changes to "Program Files"
3) Type in "cd *live" then press [TAB], then press [Enter] if the word "*live" changes to "Microsoft Windows OneCare Live"
4) Type in "SafeModeAVScanner –s –h" then press [Enter] to start the safemode anti-virus scan
