I've recently installed WWP on my new PC with specs :
Intel Core 2 Quad 2.4 GHZ, 1 GB RAM PC-5300, GeForce 8600 GT, Windows XP and I experienced slower menu loading and game loading, but the gameplay is just fine.

Compare it with my old PC with spec :
Intel Pentium 4 1.6 GHZ, 512 MB RAM (not really sure bout the timing), GeForce 2 MX, Windows XP has faster loading time and others..

How come??

Is it just the loading time that is decreased, or does it actually lag when in the menu?

If the latter, it is fixed in WA, a much better game as it is still supported through beta updates, and allows other than bugfixes, ability to record games and play them back later, ability to use colour maps of much larger sizes online, ability to minimize the game anywhere in the menu or ingame, chat pinning, weapon menu viewing when not your turn, the list goes on.

If the formewr, then I dunno, that's very weird

Highly likely the "slow menu" bug.

yes the slow menu bug.. anyway to fix?

yes the slow menu bug.. anyway to fix?
Not really.

You could revert your Forceware drivers back to 66.93, which are very old though.
You could get a different graphics card, preferrably not Nvidia but ATI, which is most likely no option for you.
You could try www.omegadrivers.net. Those 3rd party modified drivers have worked for some in the past. They are not based on the latest drivers though.
I found that the slow menus got somewhat better when I switched from a GF6600 to a GF7900GS.

Also, try adding the -nointro commandline switch to your WWP shortcut. That'll at least save you from the slow intro screens and gets you right to the main menu.
IIRC, someone reported a slight improvement when he replaced the moving cloud sprites in the background with blank ones.

Ah, yes, the favourite answer you'll get around here:
Get Worms Armageddon!
The recent beta updates have fixed that issue, plus with all the new features and bug fixes it's way better than WWP now anyway.
You can get it very cheap from the official T17 store.

!!!Warning: Do NOT buy any downloadable version of WA (Trygames/Trymedia or Gametap)! They are NOT compatible with the beta updates. Only CD versions (original or budget re-release like Sold-Out, Greenpepper).