You can't uninstall a program called smart panel because of missing uninstaller, and you can't install it, presumably because it isn't uninstalled. That's right?
Possibilities escape this catch-22 are dubious, to say the least:
1. Delete software from Explorer, clean registry with Regedit (or maybe some registry cleaner, but it's a wild guess that will work). Help by Epson might be needed to tell you what to delete.
2. Go back to previous system restore point, and hope the uninstall is still there (very uncertain).
3. Buy a Canon or HP scanner, and forget about this software on this computer. You might be able to get a reasonable price for the Epson scanner on eBay.
4. Install software on another computer, and copy uninstall information. Help by Epson might be needed to tell you what to copy.
5. Download latest driver from Epson to see if this more error-proof, so that it will install.
I'm sorry, but that's all I have to offer.
Kees