A 2400+ should easily handle XP if you work around the bottlenecks of the system.
As an experiment I set up an XP2600+ with 2Gigs of RAM and Win2k, which is known for its ridiculous boot times.
Since there's no way I'll ever come even close to using 2GB RAM in this system, I decided to create a 1GB RAMDisk for temp/cache/swap files.
The OS is installed on a cheap 4GB CF card (Transcend MLC 133x) and connected via CF>IDE adapter to the mainboard. Since it's a super cheap card, the transfer rates are terrible...not even 25MB/s.
But the system runs like it's on steroids. Loading times, workspeed etc. it's almost insane for this old rig.
Firefox5 starts in about 2.5 seconds, while my main computer (x2 5000+ with a WD Raptor system disc) takes three times as long.
The CF card + adapter from China was about 20$ total, absolutely worth it, as it boosts even outdated systems by a lot!
The low access times work wonders. I have no doubt that XP will run just as well. 1GB RAM should still be enouth, even for web applications.
One more note about the RAM:
I've got 2x1GB sticks installed and the system is quite picky. It wouldn't post with quality Corsair RAM (which works perfectly on a different board), but luckily I had some old Kingston Value DIMMs lying around, which did the trick.