Things have come a long way in 5 years but the basic tasks you are after are still the same. Photo editing is the only thing you seem to do do that would perhaps need higher level equipment than an entry level computer, and if your Celeron is handling your needs now, a new computer of any sort should be at least as good.
Apart from Dell still insisting on offering 256Mb RAM as the entry level, I suspect they would provide everything you need. Go to the web page, check out their current specials, start with the entry level poota and option it up with extra RAM and whatever you need in graphics upgrades and you should still come out with a very serviceable computer for no more than $1200. FWIW, my advice is to save money on extended warranties; whatever goes wrong with a computer seems to happen in the first few months; after that it's nearly always blamed on software you've added, which is not covered. If you do a HDD or similar in a couple of years, new components are cheaper than the warranty anyway.
I speak from the point of view of a relative dork, but I've found that's often the best advice people can get if they are closer to the bottom of the ladder than the top. Mate of mine puts together computers and says he can't do it for a better price than Dell. The OS will be XP Home, not Pro, unless for some unknown reason you want to pay more for Pro.
I've had several Dells; it's a fairly easy way of doing things. Feel free to PM me if there's anything else I can add.
P.S. I agree entirely with Conan too!