Sorry to burst your bubble Mac people but a Mac now IS simply a PC. they have exactly the same Intel CPUs and chipsets as a Dell. They are even assembled by various Taiwanese and Chinese sub-contractors who also make PCs (I think Asus is one of them). Apple also have quite a lot of quality issues currently too, from Macbook heat issues, to poor LCD screens and discolouring plastic (white models). Oh, and we won't mention the stability problems of the latest version of OSX shall we.....
All you are paying for is the OS and the design if that kinda thing floats your boat. Indeed, with a bit of effort to get around Apple's deliberate knobbling, OSX installs on A.N.Other PC.
However, in most cases hardwarewise you are actually buying somewhat outdated and slow hardware with limited options for customisation and upgrade. I can only marvel at the dumbness of their desktops permanently welding the most expensive component and otherwise re-useable item (the screen) to the actual (already obsolete) computer, ineffect creating a laptop without the convenience of being portable. Marketing idiocy 1, common sense 0.
I'm not sure what you mean by "doing" graphics but if photoshopping then that's nothing to even a bottom of the range system today.
Indeed the only reason whatsoever to buy anything other than a bottom of the range dual core with a couple of gigs memory is if you encode video (more CPU) or play games (better graphics).
For photoshop extra graphic won't buy you anything at all over even integrated graphics. although at the professional end (quadro pro, which cost £600 and I have at work) it does support hardware line anti-aliasing, which makes sod-all difference in the real world.
It often beats me why people say windows is unstable, other than some dodgy drivers (the pitfall of actually having a choice of what hardware you can use) and some ill-advised overclocking, Windows 2000 and XP has never, ever crashed on me in 8 years.
And David, your G4 was left behind by even a cheap PC somewhere around 2004, with the first die-shrink of the pentium IV (it's when Apple had to withdraw their adds for claiming they were faster, when they weren't).
Really, the only reasons to buy a Mac are if you like the style and the OS, the other reasons simple don't exist anymore, some people seem to be stuck in some kiond of weird Windows 95 timewarp. You can avoid viruses by not being an idiot and opening dodgy attachments or installing dubious freeware. anti-virus programs can be had for free. And if you think you are buying into some culture of the cool hippy little guy over big business MS, think again. Apple's restrictive practices on both their machines and their portables are far, far more fascist than anything to come out of Redmond. Don't like itunes or quicktime? (which you should as both are abysmal pieces of software). Well tough, Apple can and will deliberately break any alternative you might choose with the next upgrade.
The CPU in this machine cost about £80. It's 2 cores are running at 3.2GHz, it dual boots WinXP and SuSE Linux/KDE. The whole machine cost no more than £200 as it has the same aluminium case I bought in 2001, and the same optical drives I bought in 2005. the hard disk drive came from the previous machine as does the Graphics card, although sometimes it's swapped for a vintage Matrox G400 (2000 I think) as it does RGB out to a normal TV. To get even remotely close to this in performace you'd need a MacPro - and very probably a mortgage. Personally I'd rather not spend two grand on a type-writer internet thingy. As I spend most time on the net or skype anyway, the Os is becoming increasingly irrelevent. You can see the way things are going with web 2.0 as demostrated by youtube and google apps. Apple will be in deep doodoo, because there simply won't be any advantage in OSX, the apps are moving out of the OS. Why d'you think all the fuss is over ipods and phones and only the odd rather small update to Apple computers?