How much Ram? Given the age of the PC, if you have less than 256mb of RAM(and probably even if you have more), you might be better served by Xubuntu. It is Ubuntu, no doubt about that, will run all Ubuntu programs, etc. but it runs a much lighter desktop than Ubuntu/Kubuntu, and should suit itself well to an older PC. I put Xubuntu on a 600mhz, 256mb Ram, 20gig hard drive machine that I built several years ago, and it works very well. I have 2 machines that are 2ghz, 200gb+ Hard drive, 1gb RAM, and they both run the standard Gnome interface fine.
What type of internet connection? Some modems can be very difficult to configure in Linux if you are still on dial up.. If you have dsl/cable, then while your card may require some help to get working(all of mine have worked automatically thank goodness), it should work.
Download Xubuntu Edgy, burn it to a CDR, and restart your computer. You can run it completely from the CD to test your hardware(Net connection, Video, etc,.) If there's some really screwy problem, its a simple matter of removing the CD and restarting, and you're back to Windows, and can research the problem.