Re: Pent III 1.2 GHz or Celeron 1.4 GHz...
Sorry for the long wait. I've seen your post and nobody has answered so far. Well the difference would be great. A Celeron 1.0ghz processor compared to a 1.2ghz P3, the P3 would win hands down. The Celerons are made for basic tasks like surfing the web and word processing. The P3 is made for more multimedia related tasks. I would reccommend upgrading but not to a P3. With prices these days, you could built a world class computer at a fraction of the price, and it would perform tons better than a P3.
If you still wanted to buy the P3 however, you could look on newegg.com. I'm not sure if they even make those anymore. I'd recommend you buy a AMD 939 mobo like the ASUS SLi board, and a AMD 64 3200+. You could overclock that bad boy to a 3500+. Also, if you buy a good motherboard chances are that its intergrated graphics will be enough to handle basic games and graphic tasks. I strongly recommend getting a good graphics card though, because even the older games will only play with certain chipsets. A good card is the nVidia 6600gt, or the ATI x850xt. Both are under 200 dollars I believe. Good luck, and hope I helped.
Rig -- Emachines T5026, 3.06ghz P4, 300W Bestec PSU, 160 sata hd, 512mb dual channel 3200 ram @ 3-3-5-8, ATI Radeon 9250 pci, dual layer 16x dvd+/-rw.