I would also say there is NO DIFFERENCE whatesoever at all between retail and OEM installs. It's the same silver disk for both, it installs the same, has the same drivers, works the same way.
Where they differ is in some small things that don't really matter to the average person anyway. Ones that I can list offhand:
1: As stated many times, OEM has a different license. Most important, that it must be purchased with hardware. The hardware in question is any piece of hardware required for a system to be usable. Which can go right down the cheapest part like a bios battery or ribbon cable. This is hardly a reason to switch to retail. Nor does it limit XP's usefulness or features or anything else. It's just the way it has to be sold.
2: OEM CDs, by virtue of the aformentioned setupp.ini variables, accept only OEM product keys. This is true for any version anyway. Retail only accepts retail, and VL for VL. Also no reason to switch, unless you, for some reason, have a pile of illegal retail keys you want to use? In which case you need a retail CD. Or OEM keys, you need the OEM CD. This is no reason to switch, as each version just takes the type of code you get with it. With no advantage or disadvantage to either.
3: When you buy OEM, you only get the CD and product key, maybe with a single piece of paperwork. No box or manuals etc...And who ever read that manual? And who hangs their retail box on the wall for looks? Just extras you want to pay 10s of dollars for for nothing.
And I guess MS doesn't give support for them. But who ever tries to get support from MS when you have places like Techspot? Who would ever subject themselves to the torture of trying to get help from MS? That is no reason to get retail over OEM. So MS can say it's Norton's fault, and Norton can say it's your ISPs fault, and your ISP can say it's Windows fault and then MS will again say it's a hardware problem, and so ASUS or whatever, says it's your RAM, and Corsair says it's the CPU, and Intel says your hard drive is bad....... um, no. I wouldn't call MS support if you paid me.
Our store, just about, exclusively buys XP OEM for everything we do from selling it to building machines. And never ran into troubles because it's the SAME as retail in regards to the software itself, drivers, install process etc...
Whether you buy OEM or retail, doesn't matter, you can still only use the key you get with it, to put on ONE PC. So no advantage/disadvantage to either.
Why pay extra for a box and silly manual which tells you nothing?
I'm not advocating OEM, I'm just saying there is no difference installing windows between the two. It works exactly the same. So don't buy retail cause you think OEM is somehow a crippled version, which it is NOT.
And lastly, between Pro and Media, just so you know, unless things have changed, you can't buy Media Center, it only comes preinstalled on PCs. The average person can't walk into PCs 'r US and buy Media Center. MS only sells it en masse to PC manufacturers. Again, unless things have changed.
That's my take. Take it or leave it.