I have a 4 month old Insprion desktop with Vista Home Premium installed.Out of the blue it would not let me log on, I have administrator rights, but it said User Account Service Service failed. The Dell support team told me I had to wipe it clean and reinstall the operating system. This was a timely process and continues to be so,I have to reinstall internet service,etc.When I asked why this would happen,they said it was related to not having a security program. I didnt have this because I could not access some websites with this and it created lots of problems. My question is, Is this a problem inherent with Vista or could it be security related? I know very little about computers. I also had a dial up connection with AOL and Coppernet.

Here is some information on it. It's not inherently a security issue but it could be the result of a virus or malicious program making changes to your system.

The User Profile Service failed the logon. User profile cannot be loaded. - Vista Forums
Error message when you log on to a Windows Vista-based computer by using a temporary profile: "The User Profile Service failed the logon. User profile cannot be loaded"

If you installed, updated or changed anything right before this happened, that was likely the cause.