The specs of the PC in the link is missing a graphics card and it doesn't seem like there is one integrated into the motherboard either. The computer you have doesn't seem like it cam be upgraded any further without requiring a new motherboard and with a new motherboard, you might as well get a new PC.
What do you feel is lacking on it? Other than being a single core processor, assuming there is a graphics card on it, everything else seems fine. If you're not doing any heavy gaming (I'm talking about playing recent games at maximum resolutions and settings), then that PC should last as long as you want it to. That build should be fine for light to medium gaming, word processing and internet. I would say it would last another year or so before you actually need a new PC but don't get me wrong, that thing is getting pretty obsolete.
If anything, you probably would want a bigger hard drive. Maybe a reboot would make it seem faster too by removing all the clutter you've collected through the years. Be sure to back up your stuff first though.