Ahh, didn't realise he was on holiday (ironically, he's on holiday until my birthday

).
Ninety-Six, how are you with installing new videocard drivers? Because what you have installed at the moment is fairly outdated (it's a build from 2003). Obviously the card is also pretty old, but there are many newer drivers for it that had been released since then, the most recent being;
http://www.nvidia.co...2k_93.71_2.html
I'd recommend upgrading to those - it may provide benefits all around - not just in EDuke32 / Duke Plus.
I think you'll also find that DukePlus will hit your CPU a LOT harder than most mods, as there's just so much additional overhead involved with all the new code... Quite frankly, with that old CPU there may not be a lot you can do. I have a P4 1.8ghz machine with an FX5200 here at work, and I did try running DukePlus on it at one stage but it was unbearably slow and did take quite some time to navigate menus and even just get into the game.
Sorry, but you're probably shit out of luck in this case. EDuke32 + HRP may be fine as it is, but DukePlus could simply be putting too much load on your CPU to run smoothly. Nature of the beast and all that.