I came across this problem on a Windows 2003 server today. A client called me indicating their emails were getting delayed and the server response time logging in was very slow. So I logged in to investigate. I found the hpwebjetd.exe was taking up 100% of the processor. So I naturally terminated the application. This immediately resolved the problem temporarily.
Now for the investigation. I checked the web for this problem and I found a forum on HP’s website but it was honestly worthless. A link to it can be found here. Then I started to think to myself that this application should not be installed on the server anyways. It really makes you think how in Windows 2007 ships with nothing installed. This is actually a smart concept if you really think about it. If your server is only running the services necessary to support your needs it will be a lot more solid. So I uninstalled the hp web jet direct admin utility. I just made a server a little more stable.