FWIW, I found the eMachines website to be a slightly worthless.
I installed Win2k on my girlfriends 466 emachine a year or so ago and just recently installed XP-Pro on same with out problems.
The only issues you will have are the drives for onboard/built-in hardware. Not being familiar with your particular machine, I would search for drivers for any on-board sound/video/modem before trying the upgrade.
I think her machine had a software-based modemn that was the hardest to find drivers for, but they are out there.
With you having a newer machine, I don't think you would have any problems locating drivers. Gather all your new drivers on a 2nd partion, CD or floppies before you begin.
Just for your info, I have also installed new video & sound cards, and disabled her built-in modem on the emachine(using cable now). Using XP-Pro now on it and it handles all the driver installations flawlessly.
Good luck.
Mark