SharePoint Reset Password

Reset password
stsadm -o updatefarmcredentials -userlogin -password
stsadm -o updatefarmcredentials -identitytype NetworkService
iisreset /noforce
More Info:
http://technet.microsoft.com/en-us/library/cc288991.aspx
http://technet.microsoft.com/en-us/library/cc287638.aspx