HELP with Setting RPC Locator to Default!

Hi:

I have been having problems with getting latest updated Avast to work, as I was getting RPC error, I went into services.msc and changed setting for RPC Locator to Automatic. The default is Manual, with LogOn to NT AUTHORITY\NetworkService. But I changed it to Automatic , with LogOn to Local System. Now when I change it to default it asks me for new password, which I can set, but when I reboot the computer it does not start correctly. I tried all this SAFE Mode. I dont know the original password displayed in the LogOn screen. Now What should I do to set things to default for RPC Locator in the Admin->Services palette.

Thanks all for your help,
Alan

Make sure you are logged in as ADMINISTRATOR when trying to make the changes.