I am running into the same problem on an eMachines ET1331G. Initially, I wanted to print to an older Dell - found the driver was not Windows 7 compatible so installed my Canon PX100 successfully and used it for over a month with no problems. Then I needed to move the computer to a different desk and install a driver for an Epson NX415. Using "Add Printer", the message says "Windows can't open Add Printer. The local print spooler service is not running. Please restart the spooler or restart the machine". Restarting the machine does not resolve the problem. In Control Panel/Admin Tools/Services/Print Spooler, the spooler is set to start automatically and will sometimes show started, sometimes not. If I start it and then go back to Devices and Printers, the Epson will show that it is installed and ready. But if I then try to print something, it says "Before you can perform printer....., you must first install a printer. ...". If I logout and return later, I will find the spooler no longer running.
I have tried the latest 64 bit drivers from Epson with no success. I am running Windows 7 Home Premium 64 bit.