Breaking It In Two
Don't Mix Business and Pleasure
From your letter I can guess that you are really running this one machine ragged doing both massive amounts of schoolwork, office work, and gaming on the same rig.
Based upon your needs, I would say that building a second rig, and dedicating one to gaming and the other to office work is the way to go for you. Considering that you are talking about going with a new board and CPU(s), and the sheer amount of current hardware you own already, I am thinking that you are already halfway to having another system together. So that is a much more realistic option, and it will probably be more effective for your needs as well. Read on to learn why.
One for Work, One for Play
You already have a TON of RAM (512MB, yikes) so dropping 256MB in one machine and 256MB in the other would not be a problem at all, and would be MORE than enough to keep both systems happy. I would recommend getting another case of your liking, dropping the DVD and Burner into that machine and use it for your office and movie watching duties, while the other one can be used solely for your gaming. This would be an effective solution for you because now you will be isolating your work from your gaming, making the likelihood of a device or software failure less of a possibility from simple overwork of the machine. Even if something catastrophic DOES happen from your recent installation of the latest leaked GeForce Beta Drivers, your work is safe and sound on the other machine.
Sounds Like a Plan, Stan. What should I buy?
What hardware to buy is really going to be a personal choice, but considering your needs, you are going to want a decent amount of horsepower in each system. As always, I will recommend that you NOT wait for next generation hardware, mainly because no matter how long you wait, there will
**Always** be some new Next-Gen piece of hardware on the horizon ready to make you salivate. Besides that, just about anything you build now is definitely going to be able to get the job done, and VERY well if I may add.
Celeron or PIII? That is the question!
I would think that anything 450 and up will do you just fine; I myself am running a PIII 450 without any problems with only minor in-game slowdowns, but since you don't state your budget, it's really tough to make some solid suggestions for you.
A quick search on Pricewatch reveals that a PIII 450 OEM can be had for about $170-180, and the PIII 500 is priced right now just above the paltry sum of $200, the 550 however leaps up in the air at about $340, making it out of reach in my opinion. Taking those amounts into account, I would most likely shoot for the PIII 500 myself. Mainly because it's not priced too much above the 450, and I think the performance difference would be worth it as well.
Then again, if you are looking to go even cheaper, and don't mind the 66Mhz bus, you can snag a Celeron 500 for the measly sum of around $130!! That is a fantastic price for a very capable CPU. The Celeron would make a nice gaming rig that would perform very close to its big brother the PIII, mainly because caching schemes don't matter all that much with 3D geometry where data is constantly changing. Caching information in that respect doesn't make any real difference at all. You can build a very solid gaming rig for a very cheap price.